In high-low temperature experiments,the null shift of the four-mode laser gyro whose beam intensity is stablely controlled in two different modes is very different.The null shift vibrates in one mode but changes linearly with temperature in the other one.Aiming at this phenomenon,through the analysis based on the basic theory,the physical reason that the differential lose null shift and the constant magnetism biasing null shift change differently with temperature in different modes is found.If using temperature compensation to improve the precision of the four-mode laser gyro,the coefficient must be gotten in the same mode which is selected by actual use.