To improve the locating accuracy of quadrotor indoor, a locating algorithm based on vision is presented. Reference lines should be set on the ground and its color is different with ground, and quadrotor vision sensor is used to acquire images. Extract the reference line features, locates the relative positions between quadrotor and reference lines and compumds it with micro-inertia measuring unit data for actual position of the quadrotor. AR.Drone is used for validating this method and the result shows that this algorithm can realize high accuracy location meet accuracy requirements of trajectory tracking of quadrotor