The accuracy of geomagnetic reference map, geomagnetic sensor, and inertial navigation system is the key factor which affects the reliability of magnetic contour matching (MAGCOM) system. In order to improve the reliability of MAGCOM, the influence of the sensor's accuracy on the matching success rate has been studied. For different geomagnetic reference maps, the factors and their physical mechanism affecting matching success rate have been analyzed, the factors are geomagnetic sensor error, velocity error, and heading angle error. The error range of sensors was determined by the simulation computing which was based on a practical system and a simulation experimentation was implemented by using the geomagnetic reference map. The simulation results show that MAGCOM can allow the velocity error 0.14 m/s, the heading angle error 0.6 and the standard deviation of geomagnetic sensor noise 11 nT, when the matching success rate is 90%.