Quadrotor is a kind of common helicopter, which has non-linear and multi-variable coupling characteristics. Based on the simplified mathematical model of quadrotor, the attitude control can be divided into several parts, which are independent each other. Developing the traditional PID controller, a Fuzzy-PI controller is designed by combining a fuzzy controller with a PI controller. The simulation results show that the new Fuzzy-PI method not only satisfies static-state accuracy, but is better than the traditional PID controller in over shoot value, rise time and transition time of quadrotor attitude control system.