The invention discloses a rock thermophysical property testing system under the deep sea high-pressure condition.The rock thermophysical property testing system comprises two pressure-resisting tanks, a data collecting unit is installed in the first pressure-resisting tank, a cavity of the second pressure-resisting tank is filled with sea water and internally provided with a rock sample, a first temperature sensor and a second temperature sensor are installed in the center and on the outer surface of the rock sample respectively, a third temperature sensor and a pressure sensor are installed in the cavity, output ends of the first temperature sensor, the second temperature sensor, the third temperature sensor and the pressure sensor are connected with the input end of the data collecting unit through watertight cables, and a drain valve communicated with the cavity is installed on the second pressure-resisting tank.The invention further discloses a rock thermophysical property testing method under the deep sea high-pressure condition.An electric heating heat source or a booster pump is not needed, the rock sample is loaded instantly by fast switching on the drain valve, and the thermophysical property of the rock sample can be obtained by using a set finite element quantitative value inversion model.