Micro Air Vehicles(MAV) are characterized by their small sizes,low powers and load ability,so it is difficult to obtain the full state measurements in real time and short of a full control degree.In order to solve the problems of autonomous fight control and stability,this paper presents a guidance algorithm for the relative miniature GPS-based navigation system of an electrically MAV. One standard geometric method for solving autonomous flight is adopted to derive a class of algorithm based on the heading angle error and yawing distance error and the MEMS sensors are used to design a flight control system.Simulation and practical experiments show that the guidance algorithm used in the MAVs is effective with different PID controlling parameters,which can obtain a yawing distance error less than 30 m.The TH680 equipped with the GPS-based autonomous flight control system loading the designed geometric algorithms has been successfully tested in a flight,and the yawing distance error is less than 30 m in a 2 level wind.