The invention discloses an outdoor protection device and method for precision hydraulic components of a shield tunnel test platform, characterized in that the device comprises a physical isolation boxof which the interlayer is filled with a thermal insulation layer, wherein a temperature sensor is arranged in the physical isolation box, a closed constant temperature regulating device is arrangedbetween a hot air inlet and a cold air inlet on the physical isolation box, and the closed constant temperature regulating device comprises a booster pump, a first selective adaptation valve, a secondselective adaptation valve, a first cut-off valve, a second cut-off valve, a self-circulation heater and a semiconductor refrigerator; an air filter is connected with the closed constant temperatureregulating device through a pressure supplementing valve, the booster pump, the first cut-off valve, the self-circulation heater, the physical isolation box and the first selective adaptation valve are connected to form a closed heating circulation loop, and the booster pump, the second cut-off valve, the semiconductor refrigerator, the physical isolation box and the second selective adaptation valve are connected to form a closed cooling circulation loop. The scheme of the invention has the advantages of realizing heat insulation and cold insulation and performing constant temperature controlthrough the closed circulation loop.