A cooling system (1, 1a) for power modules, characterized by comprising: two covers (11, 12); a plurality of power modules disposed between the two covers (11, 12) and arranged in sequence, wherein each of the plurality of power modules comprises a housing, a circuit board and a plurality of heat dissipation elements, the circuit board is engaged in the housing, the plurality of heat dissipation elements are disposed on the two sides of the circuit board, and there is a through hole on the housing; and a plurality of first spaces, wherein each of the plurality of first spaces is formed between the cover (11, 12) and the neighboring power module, wherein the plurality of heat dissipation elements of each of the plurality of power modules are located in the neighboring first spaces, and the through hole of each of the plurality of power modules are in communication with the neighboring first spaces, wherein the plurality of first spaces and the through holes of the plurality of power modules are communicated with each other to form a coolant passageway collaboratively for allowing a coolant to pass through, wherein the two covers are a top cover and a bottom cover, the top and bottom covers (11, 12) have a coolant outlet and a coolant inlet respectively, the coolant inlet is in communication with the first space formed between the bottom cover and the neighboring power module and is configured to introduce the coolant into the coolant passageway, and the coolant outlet is in communication with the first space formed between the top cover and the neighboring power module and is configured to release the coolant from the coolant passageway, wherein centers of the two covers (11, 12) are both located on a first direction, and the plurality of power modules are disposed along a second direction perpendicular to the first direction in sequence, wherein the cooling system further comprises a first spacer, the first spacer is disposed between the top cover and the plurality of power modules, the top cover comprises a third space in communication with the coolant outlet, the first spacer has a plurality of openings corresponding to and communicating with the first spaces formed between the top cover and the plurality of power modules respectively, and the plurality of openings of the first spacer is in communication with the third space, wherein the cooling system further comprises a second spacer, the second spacer is disposed between the bottom cover and the plurality of power modules, the bottom cover comprises a fourth space in communication with the coolant inlet, the second spacer has a plurality of openings corresponding to and communicating with the first spaces formed between the bottom cover and the plurality of power modules respectively, and the plurality of openings of the second spacer is in communication with the fourth space. two covers (11, 12); a plurality of power modules disposed between the two covers (11, 12) and arranged in sequence, wherein each of the plurality of power modules comprises a housing, a circuit board and a plurality of heat dissipation elements, the circuit board is engaged in the housing, the plurality of heat dissipation elements are disposed on the two sides of the circuit board, and there is a through hole on the housing; and a plurality of first spaces, wherein each of the plurality of first spaces is formed between the cover (11, 12) and the neighboring power module, wherein the plurality of heat dissipation elements of each of the plurality of power modules are located in the neighboring first spaces, and the through hole of each of the plurality of power modules are in communication with the neighboring first spaces, wherein the plurality of first spaces and the through holes of the plurality of power modules are communicated with each other to form a coolant passageway collaboratively for allowing a coolant to pass through, wherein the two covers are a top cover and a bottom cover, the top and bottom covers (11, 12) have a coolant outlet and a coolant inlet respectively, the coolant inlet is in communication with the first space formed between the bottom cover and the neighboring power module and is configured to introduce the coolant into the coolant passageway, and the coolant outlet is in communication with the first space formed between the top cover and the neighboring power module and is configured to release the coolant from the coolant passageway, wherein centers of the two covers (11, 12) are both located on a first direction, and the plurality of power modules are disposed along a second direction perpendicular to the first direction in sequence, wherein the cooling system further comprises a first spacer, the first spacer is disposed between the top cover and the plurality of power modules, the top cover comprises a third space in communication with the coolant outlet, the first spacer has a plurality of openings corresponding to and communicating with the first spaces formed between the top cover and the plurality of power modules respectively, and the plurality of openings of the first spacer is in communication with the third space, wherein the cooling system further comprises a second spacer, the second spacer is disposed between the bottom cover and the plurality of power modules, the bottom cover comprises a fourth space in communication with the coolant inlet, the second spacer has a plurality of openings corresponding to and communicating with the first spaces formed between the bottom cover and the plurality of power modules respectively, and the plurality of openings of the second spacer is in communication with the fourth space.