Abstract: Genetic algorithm（GA） is an efficiently combined and optimized method by simulating the nature evolution. The paper studies the optimization criterion of PID controller, introduces the fundament of GA, and gives the approach to optimize PID controller parameters using GA. The paper also gives an example applying GA to optimize a PID controller of a single loop system. The simulation result gives the possibility and practicability of optimized PID controller with GA. GA overcomes some disadvantages of other ways.