The compensation model and biasing theory were investigated to improve the precision of Zeeman laser gyroscope. Based on the output characteristic of laser gyro, the optimal number of the compensation model was deduced. It was found that the Zeeman biasing value can be considered to depend linearly on the internal temperature among the operational temperature. That is why it is potential to utilize the biasing value for correction model to compensating the zero drift of laser gyro changing with temperature. The precision of zeeman laser gyro was improved greatly by the compensation model based on Zeeman biasing value. The compensation model can represent the output error of laser gyro accurately. Results of experiments prove that the compensation model on biasing value is greatly valuable to practical engineering application.