In order to research the influence of inner heat sources on the Mechanically Dithered Ring Laser Gyroscopes (MDRLGs), a temperature field model is established with finite element software ANSYS to simulate the temperature fields.Firstly, the finite element model is simplified, and then the disposal of material parameters, calculating methods of heat generation rate and the heat transfer coefficients are explained.Finally, the steady-state temperature field and the transient temperature field in 1 h and 3 h are given,which indicates the highest and lowest temperature regions and the distribution of a temperature gradient.A circuit to measure temperature using a platinum resistor is designed, and its precision is 0.005 ℃.The simulated results are compared with experimental ones and the error is less than 2%, which validates the rationality of the model.This research provides some helps for the selection of the temperature testing points, and improves the effect of temperature compensation for MDRLGs.