The invention discloses a thermal distortion compensation device of a disk laser amplifier. The thermal distortion compensation device comprises a temperature control mechanism and a gain medium, wherein the space between the temperature control mechanism and the gain medium is filled with heat conducting silicone grease; the temperature control mechanism comprises an annular heat sink copper block, a heater and a heat insulator; the aperture of the annular heat sink copper block is matched with the aperture of the gain medium; the heater is fixed in the annular heat sink copper block; the heat insulator is fixed on the periphery of the annular heat sink copper block. The thermal distortion compensation device is simple in structure, easy to assemble, high in university and applicable to thermal distortion compensation of disk laser amplifiers with various laser energy and spot sizes, the thermal management effect of the disk laser amplifier is improved, real-time adjustment can be carried out, thermally induced wavefront distortion of the disk laser amplifier during repetition frequency operation can be reduced, and the compensation effect is good.