The AFA 3 G grid is the key component of the fuel assembly. The tensile breaking force of the A-A’ cross welding point directly affects the strength of the grid frame and the safe operation of the fuel assembly in the nuclear reactor. Starting with the structure composition and electron beam welding principle of the electron beam welder,this paper analyzes the stability of the tensile breaking force of the solder joint through the statistics and calculation of the tensile breaking force of the A-A’ cross welding point,according to the fluctuation of the tensile breaking force of the solder joint,and takes the pertinent measures and carries out the test.The test results show that the cause of the fluctuation of the tensile breaking force of the A-A’ cross welding point is systematic,but the main and key reason is the change of the distance between the cathode and the grid. In the process of production,it is effective to control the shape and size of A-A’ cross solder in time and measure and control the distance between the cathode and grid,and then take 220 h to replace the cathode to control the tensile breaking of the A-A’ cross welding point.