Abstract: For analyzing the thermal effect in thin disk laser, a numerical model of the thin disk laser medium end-pumped by LD was set up. Considering the influence of the temperature correlation of the thermodynamic parameters of the material and the heat transfer coefficient between air and medium, based on the thermal conduction equations and the thermal-elastic equations, the transient distributions of temperature and thermal stress in the medium were calculated by a finite element analysis method. The influence disciplinarian of the pump power and heat transfer coefficient and time on transient distributions of temperature and thermal stress in the medium were analyzed. Simulation results indicate that thermal extendable damage appears on the edge of beam of the anterior surface. The change of the rise time and renew time of the temperature and stress is not obvious as the pumping power increase. With the increase of the heat transfer coefficient, the temperature and stress and rise time and renew time decrease, but this rate of the change decreases to zero slowly. The theoretical results agree with interrelated experiment results and it provides a theoretical reference for the design of solid laser pumped by LD and experimental analysis.