Abstract: Simulated annealing algorithm have been applied to optimize design of wet multiple brakes involving the mixing design variable on the combination of continuous and discrete design variable. Simulated Annealing Algorithm to be improved was applied to optimize design of multi-objective functions on wet multiple brakes, which may obtain satisfactory optimum design result. The optimum design results indicate that simulated annealing algorithm, which is applied to optimize design of wet multiple brakes, is feasible and high effective. This algorithm may be applied to optimize design of engineering structure widely.