A precise model for the common rail fuel injector based on the Matlab/Simulink was built. Using the multi objective simulated annealing algorithm as the search strategy, the key injector parameters were optimized. The aim function of the multi objective optimization was the opening delay and the closing delay. The results showed that the delay of the opening was 0.25ms which reduced by 16.7%; while the delay of the closing was 0.78ms, which reduced by 15.2%. 