Abstract: Indoor quadrotor with the speed of conventional inertial measurement unit to collect speed data has great error, unable to point in the process of actual flight hovering. Aiming at this problem based on vision, a set of small indoor four rotor aircraft is built, with the application of cascade ratio PID (Proportion Integration
Differential) control algorithm. The experimental results show that it effectively solves the indoor or closed environment in the process of the four rotor in hovering flight level drift problem, making the four rotor aircraft flying in the indoor environment smoothly.

Key words: stable flight, quadrotor, proportion integral differential(PID), visual servo control