Based on the fundamental theory of heat transfer in cylinder, the transient temperature field in the laser crystal of pulsed laser diode (LD) end-pumped Nd∶YAG laser is analyzed by the finite-element method. The temperature distribution of crystal end surface in the process of temperature rise and fall is calculated in a single pulse process. The influences of beam waist width and its location on the temperature distribution and the factors influencing the thermal relaxation time are presented. Based on the theory of ray trace, the time variation of optical path difference at the center and fringe of crystal end surface caused by temperature gradient after the temperature distribution in the crystal reaches a dynamic balance is analyzed. The results show that the increase of beam waist width or rearward shift the beam waist without changing beam waist width will reduce the end surface temperature when the laser beam waist is located on the pumped end surface. Increasing the heat transfer coefficient of cooling liquid or flow velocity of air, reducing the air temperature or the radius of laser crystal can shorten the thermal relaxation time. After the transient temperature distribution reach a dynamic balance, the temperature in crystal and relative optical path difference (OPD) caused by radial temperature gradient will periodically change with time.