Abstract: The thermal deformation of grids assembly is the main factor affecting the working performance and working life of the ion thruster. In order to study the distribution and variation of the temperature field in the process of grids assembly heating, the method of accurately simulating the grid temperature field is explored. The full size finite element model of the 1/12 grids assembly is established for the heat transfer analysis. Meanwhile, the temperature measurement platform built in the laboratory, the transient temperature changes of the grids assembly in the atmosphere are measured. Comparison between the finite element analysis and test results shows that, the average error of the accelerated grid is 14.4%, the average error of the screen grid is 9.7%, the maximum error of two grids is less than 18.4%, and the credibility and rationality of the finite element model and the method is verified.