Since the influences of ambient magnetic field and manufacturing process are not taken into consideration in an electromagnetic positioning system, the positioning precision of the system may decrease.This paper presents a method to improve the positioning precision of the electromagnetic positioning system.To overcome the shortcoming that the classical magnetic dipole model is too ideal, an error correction model was proposed.The antenna calibration theory was presented, the calibration method, correction factor, calibration process and device were given.Comparative experiments show that the precision of the improved system positioning model is 5 times of the uncorrected one.