A security inspection apparatus (100, 200) configured to inspect two parts of an object, comprising: a bottom plate configured to carry the object; four two-dimensional multiple-input multiple-output array panels, each comprising: at least one two-dimensional multiple-input multiple-output sub-array, wherein each two-dimensional multiple-input multiple-output sub-array comprises a plurality of transmitting antennas and a plurality of receiving antennas, a midpoint of a connection line between each transmitting antenna of the plurality of transmitting antennas and a corresponding receiving antenna of the plurality of receiving antennas serves as an equivalent phase center, and the plurality of transmitting antennas and the plurality of receiving antennas are arranged such that the equivalent phase centers are arranged in a two-dimensional array; and a control circuit configured to control the plurality of transmitting antennas to transmit a detection signal in a form of an electromagnetic wave to the object in a preset order, and to control the plurality of receiving antennas to receive an echo signal from the object, wherein the detection signal is a microwave millimeter wave with a frequency in a range of 10 GHz - 300 GHz; one of the four two-dimensional multiple-input multiple-output array panels installed inside or below the bottom plate and parallel to the bottom plate, a signal processing device connected to the two-dimensional multiple-input multiple-output array panel and configured to reconstruct an image of the object according to the echo signal received; a display device connected to the signal processing device and configured to display a reconstructed image of the object; and at least one side plate (11, 12, 13) perpendicular to the bottom plate, characterized in that each side plate (11, 12, 13) is provided with one of the four two-dimensional multiple-input multiple-output array panels (20b, 20c, 20d), wherein the at least one side plate (11, 12, 13) comprises a first side plate, a second side plate and a third side plate, a first detection space is formed between the first side plate and the second side plate, and a second detection space is formed between the second side plate and the third side plate, wherein the first detection space and the second detection space respectively accommodate the two parts of the object. a bottom plate configured to carry the object; four two-dimensional multiple-input multiple-output array panels, each comprising: at least one two-dimensional multiple-input multiple-output sub-array, wherein each two-dimensional multiple-input multiple-output sub-array comprises a plurality of transmitting antennas and a plurality of receiving antennas, a midpoint of a connection line between each transmitting antenna of the plurality of transmitting antennas and a corresponding receiving antenna of the plurality of receiving antennas serves as an equivalent phase center, and the plurality of transmitting antennas and the plurality of receiving antennas are arranged such that the equivalent phase centers are arranged in a two-dimensional array; and a control circuit configured to control the plurality of transmitting antennas to transmit a detection signal in a form of an electromagnetic wave to the object in a preset order, and to control the plurality of receiving antennas to receive an echo signal from the object, wherein the detection signal is a microwave millimeter wave with a frequency in a range of 10 GHz - 300 GHz; at least one two-dimensional multiple-input multiple-output sub-array, wherein each two-dimensional multiple-input multiple-output sub-array comprises a plurality of transmitting antennas and a plurality of receiving antennas, a midpoint of a connection line between each transmitting antenna of the plurality of transmitting antennas and a corresponding receiving antenna of the plurality of receiving antennas serves as an equivalent phase center, and the plurality of transmitting antennas and the plurality of receiving antennas are arranged such that the equivalent phase centers are arranged in a two-dimensional array; and a control circuit configured to control the plurality of transmitting antennas to transmit a detection signal in a form of an electromagnetic wave to the object in a preset order, and to control the plurality of receiving antennas to receive an echo signal from the object, wherein the detection signal is a microwave millimeter wave with a frequency in a range of 10 GHz - 300 GHz; one of the four two-dimensional multiple-input multiple-output array panels installed inside or below the bottom plate and parallel to the bottom plate, a signal processing device connected to the two-dimensional multiple-input multiple-output array panel and configured to reconstruct an image of the object according to the echo signal received; a display device connected to the signal processing device and configured to display a reconstructed image of the object; and at least one side plate (11, 12, 13) perpendicular to the bottom plate, characterized in that each side plate (11, 12, 13) is provided with one of the four two-dimensional multiple-input multiple-output array panels (20b, 20c, 20d), wherein the at least one side plate (11, 12, 13) comprises a first side plate, a second side plate and a third side plate, a first detection space is formed between the first side plate and the second side plate, and a second detection space is formed between the second side plate and the third side plate, wherein the first detection space and the second detection space respectively accommodate the two parts of the object.