Abstract: The thermal effect of the medium in the end-pumped Nd:YAG thin-disk laser on the wavefront distribution was studied, and the calculation expression of the beam distribution in the thin-disk laser was provided. The wavefront distributions of the thin disk pumped by the ideal beam and 4th order super-Gaussian beam were simulated. The relationships between the beam distortion and the laser medium thickness and uniformity of the pumped beam were analyzed. The results show that the thiner the thin-disk is, the more uniform the pumped beam is and the smaller the pump power density is, the smaller the beam distortion is. Compared with the thin-disk thickness and the pump power density, the influence of the intensity distribution of the pumped beam on the wavefront distributioin was greater.