With the research background of the rotorcraft flying robot's integrated navigation system, an error calibration method for electric magnetic compass is proposed. Based on the analysis of the magnetic compass's measurement theory and error sources, 5 main factors which affect the heading angle calculation precision of the magnetic compass, are summarized. In response to the mentioned error factors, software and hardware solutions are proposed. Considering the specialties of rotorcraft flying robot, a simplified calibration method for magnetic compass is proposed to calibrate the hard magnetism errors and scale factor errors. The simplified magnetic compass calibration method can avoid sticking up the robot during calibration process, but its calibration precision is not decreased. The actual calibration test of the magnetic compass shows that the proposed calibration method can effectively correct the measurements' ellipsoidal distribution of the original magnetic field, and it also can improve the heading angle calculation precision of integrated navigation system. This method can simplify the calibration process and avoid to stick up the huge robot.