The invention discloses a temperature-controllable gas insulation performance testing system and a method thereof. The temperature-controllable gas insulation performance testing system comprises a gas insulation performance testing device, a high-low temperature control box and a temperature and pressure monitoring device; the gas insulation performance testing device comprises a testing electrode, a testing cavity, a high-voltage bushing and an electrode adjusting device, and the testing electrode is arranged in the testing cavity; the testing cavity is formed in the high-low temperature control box, the upper end of the testing cavity is connected with the lower end of the high-voltage bushing, and the high-low temperature control box enables the temperature of gas in the testing cavity and the temperature in the high-low temperature control box to be consistent in a heat conduction mode; gas insulation performance testing under different temperature conditions, different gas inflation pressure conditions, different voltage type conditions and different electric field ununiformity conditions can be conducted, and gas insulation performance testing at different mixing proportions of mixed gas can also be conducted; the insulation performance of different gases under the same testing conditions is compared, and a testing platform and a method thereof are provided for research of various mixed gases and replacing gases thereof.