A method for improving fire prevention performance of a vehicle-carried data recording device, comprising: - firstly, mounting the vehicle-carried data recording device in a water-proof shell in a sealing manner, a shock pad being mounted on the outside surface of the water-proof shell; - secondly, mounting the water-proof shell into an interior cavity of a constant-temperature water shell assembled of two distinct components named as upper constant-temperature water shell and lower constant-temperature water shell, the spaced enclosed by the upper and lower constant-temperature water shells (41, 42) after the assembly forming said interior cavity of the constant-temperature water shell; - thirdly, injecting water or an anti-freezing solution with water as a main component into the constant-temperature water shell, to protect the vehicle-carried data recording device from outside heat by absorbing the heat through water evaporation, the steam generated being able to escape out of the constant-temperature water shell through air outlets provided therewith; and - finally, placing the constant-temperature water shell in a protective housing provided with heat dissipation holes to prevent the data recording device from being damaged when the vehicle is damaged by the action of an external force and to improve impact resistance of the data recording device, wherein the method further comprises: packing the constant-temperature water shell in a fire-proof box made of nano-based insulation board before it is placed in the protective housing; the fire-proof box consisting of a box body (51, 54) and a box cover (52, 53), one or more of five surfaces composing the box body (51, 54) being movable blocks, connecting preventing anti-reset springs to the movable blocks and to the protective housing, the springs being configured to push the movable blocks toward the bottom surface of the box body, fixing the movable blocks to the protective housing via hot-melt plastic screws to form a heat dissipation port between the movable blocks and a bottom surface of the box body, the heat dissipation port overlapping the heat dissipation holes, the hot-melt plastic screws being configured to maintain the heat dissipation port open in the absence of fire and to melt in case of fire for automatic closing of the heat dissipation port by the movable blocks in combination with the springs, and providing retaining pin holes on the movable blocks, configured to match retaining pins mounted on the constant-temperature water shell when the heat dissipation port is closed, locking the position of the movable blocks. - firstly, mounting the vehicle-carried data recording device in a water-proof shell in a sealing manner, a shock pad being mounted on the outside surface of the water-proof shell; - secondly, mounting the water-proof shell into an interior cavity of a constant-temperature water shell assembled of two distinct components named as upper constant-temperature water shell and lower constant-temperature water shell, the spaced enclosed by the upper and lower constant-temperature water shells (41, 42) after the assembly forming said interior cavity of the constant-temperature water shell; - thirdly, injecting water or an anti-freezing solution with water as a main component into the constant-temperature water shell, to protect the vehicle-carried data recording device from outside heat by absorbing the heat through water evaporation, the steam generated being able to escape out of the constant-temperature water shell through air outlets provided therewith; and - finally, placing the constant-temperature water shell in a protective housing provided with heat dissipation holes to prevent the data recording device from being damaged when the vehicle is damaged by the action of an external force and to improve impact resistance of the data recording device, packing the constant-temperature water shell in a fire-proof box made of nano-based insulation board before it is placed in the protective housing; the fire-proof box consisting of a box body (51, 54) and a box cover (52, 53), one or more of five surfaces composing the box body (51, 54) being movable blocks, connecting preventing anti-reset springs to the movable blocks and to the protective housing, the springs being configured to push the movable blocks toward the bottom surface of the box body, fixing the movable blocks to the protective housing via hot-melt plastic screws to form a heat dissipation port between the movable blocks and a bottom surface of the box body, the heat dissipation port overlapping the heat dissipation holes, the hot-melt plastic screws being configured to maintain the heat dissipation port open in the absence of fire and to melt in case of fire for automatic closing of the heat dissipation port by the movable blocks in combination with the springs, and providing retaining pin holes on the movable blocks, configured to match retaining pins mounted on the constant-temperature water shell when the heat dissipation port is closed, locking the position of the movable blocks.