Based on the derivation of analytical formulae for electromagnetic force and thermal stress, ANSYS finite-element simulation software was used to analyze the electromagnetic-temperature-structure coupling of copper skin at the fixed top and bottom end surface. The distribution of thermal stress and the total stress and strain were obtained. The structure of reactor was further optimized, and the optimum design of the reactor was determined by taking the structural strength requirements and the temperature requirements into consideration. The credibility of simulation and design solution was verified by carrying out a test.