Abstract: In this paper, a robot arm is studied, as a typical spacecraft component. The fluid-thermal-structure coupling simulation method is used to analyze the effect of variable ventilation velocities for the test box on the ambient low temperature thermal deformation of the robot arm in the single ventilation manner. Then, the verification test is carried out. Finally, it is found that, along with the rising of the ventilation velocity, the arm temperature will have a better distribution and is more likely to reach the required temperature value, as is beneficial to the test implementation. But, due to the disturbance of the environmental noise, the arm deformation should be measured after the stabilized conditions are reached. The analysis results can be used to guide the implementation of the ambient low temperature thermal deformation test for the spacecraft components toward better accuracy and efficiency.