The grid assembly is the core component of the ion thruster. And the multilayer grid structure it contains will undergo thermal deformation during the working process, resulting in the changes of the grid spacing, and then affecting the working performance and life of the ion thruster. In order to realize the non-contact measurement and evaluation of thermal deformation of grid structure under real working conditions, an observation method of grid deformation based on camera measurement is proposed which enables to evaluate the effects of different image analysis methods (grayscale center of gravity, circle fitting, and grayscale matching) on the accuracy of deformation measurement. The results show that the grayscale matching method has high observation accuracy and good environmental adaptability. Additionally, a set of grid thermal deformation environment simulation and deformation measurement system is designed and implemented, which can realize high-precision observation of deformation under conditions of high temperature, water circulation and air circulation. Finally, the effects on the accuracy of deformation measurement under the conditions of water circulation and air circulation in the environmental chamber are evaluated, and the results indicate that both of the two conditions affect the measurement accuracy, and the effect of water circulation on the experimental results is more significant than that air circulation.