Abstract: The low pressure and temperature control facility can be used to simulate the environment of the near space, characterized by low pressure and high & low alterating temperature. First, the control of the temperature field concerns a main technical specification of the low pressure and temperature control system, which is relatively difficult. The environmental temperature in the low pressure chamber without fan is numerically simulated by the software Fluent, and the effect of the opening hole in the heat sink on the environment temperature inside the chamber is studied, then the fan model is added to the low pressure chamber, and the effect of the forced-convection heat transfer on the low pressure chamber is analyzed. The temperature control test in the low pressure chamber without the forced-convection heat transfer is completed, to evaluate the influening factors such as the cooling rate, the chamber pressure, and the test pieces and the toolings. Simulation and test result all indicate that the hole in the heat sink, the disturbance of fan, the pressure of the chamber, and the test fixtures all have some effect to the environmental temperature of the low pressure chamber. Those factors should be considered integratedly in the development of low pressure and temperature control facility.