A new profile design method for SRM nozzle was proposed, and the profile optimization was completed to improve the nozzle performance. Bi-cubic spline was used to construct the nozzle divergent section profile. Two-dimensional compressible axisymmetric N-S equations were used to do the numerical simulation with considering the coupling effects of gas flow and heat transfer. Finally, the adaptive simulated annealing algorithm was used to complete the profile optimization, with the objectives of the maximum thrust and minimum total pressure loss. The optimization increases the axial thrust of engine by 2.38%, and enhances the total pressure recovery coefficient by 2. 22%. The result shows that the shortened nozzle has much better performance than conical nozzle when they are the same long as divergent section. The result also shows that the nozzle performance can be improved through the optimization of section profile.