The thermal conduct model of laser crystal was established. Using Possion equation, the temperature and temperature distribution in laser crystal were obtained, and the optics path difference (OPD) induced by end-face deformation and total OPD were caculated. Based on the former calculation, the focal length of laser crystal with different pumping powers was obtained. The experimental result agrees with the caculated result very well. When the pumping power is 10 W and the radius of pumping beam is 320 μm, the OPD induced by end-face deformation is 45% of the total OPD for Nd:YVO4 crystal. When the pumping power is 24 W, the focal length of crystal is 65.8 mm. The end-pumped resonators with one highly reflective coating directly on the laser crystal can aggravate its thermal effect. The study shows that, for the solid-state laser with high power, the OPD induced by end-face deformation has a large influence on thermal effect of laser crystal. This study provides a theoretical direction for improving the stability of laser and studying the thermal effect of laser crystal.