Abstract: The paper presents a design and theoretical analyzes of heat switch which is based on shape memory alloy（SMA）for Spaceflight thermal control.The SMA elements in such actuators integrate both sensory and actuation functions.The SMA element start to change its shape and push heat switch to close when temperature exceeds austenite transformation point of SMA material;and while temperature decrease less than martensitic transformation point of SMA material,the bias spring is going to overcome thrust force of the SMA element and push heat switch to turn off.The structure of heat switch is cylindrical with the length of 32 mm,diameter of 23 mm.The analyzes of mechanical parameters and heat transfer performance show that the thermal resistance of this heat switch is about 2.69 K/W when close and more than 352.64 K/W when turn off,the time needed from "OFF" state to "ON" state is less than 30 min.