The research on startup null drift performance of four-frequency differential laser gyro is very valuable to the fast startup situation. Based on the process of warming-up,physical mechanism were analyzed,some affecting factors of null drift were discussed,and then the corresponding solutions were introduced. For example,we adopt dispersion equalization technology to decrease the sensitivity of gyro drift to frequency stabilizing position,auto-gain control loop to stabilize the light intensity,space non-planar cavity structure to eliminate the effect of quartz crystal,suitable design of thermal arrangement to speed up the heat balance process,reliable detecting circuits to enhance the stability,related measures to minimize the cavity distortion and so on. Experimental results show that these solutions are effective to improve the startup null drift performance of laser gyro,which are helpful to researchers.