The invention discloses a geomagnetic parking space detection method. The method includes the steps that S1, geomagnetic data is collected; S2, the geomagnetic variation Ts is calculated; S3, the zi-axis fluctuating quantity delta theta i is calculated; S4, whether the Ts is larger than the minimum noise threshold Tn or not is judged, and if yes, S5 is executed; S5, whether the delta theta i is larger than the z-axis fluctuation threshold value theta n or not is judged, and if yes, S6 is executed; S6, whether the Ts is larger than the vehicle reference quantity Th or not is judged, and if yes,S7 is executed; S7, whether a vehicle ruler is recorded or not is judged, if not, S8 is executed, and if yes, S9 is executed; S8, whether the Ts is smaller than the Th or not is judged, and if yes, S10 is executed; S9, whether the Ts is larger than the Tn or not is judged, and if yes, S11 is executed; S10, whether the z-axis change direction is opposite to the that when a vehicle exists, and if yes, the vehicle leaves; S11, whether the delta theta i is larger than the theta n or not is judged, and if yes, S12 is executed; S12, whether the Ts is smaller than the Th or not is judged, if yes, S10 is executed, and a vehicle-free ruler is updated and recorded. According to the method, on the basis of setting threshold value comparison, entering into and exiting from a parking space of the vehicle are judged by detecting the fluctuation angle of the z axis, so that the stability and accuracy of detection results can be improved.