According to the management mode of the heat capacity laser, the crystal thermal model of the pump stage and the cooling stage are established respectively by analyzing actual working characteristics of microchip laser crystal. Then the equation of the heat transfer coefficient is introduced and the expressions of the temperature field of heat capacity laser are obtained with the status of side-end-pumping and cooling of laser diode (LD). The factors of spot radius and pump time that influencing the crystal temperature field are analyzed respectively. The results show that when the thermal conductivity of Nd∶YAG crystal is constant and variable, the maximum temperature rises of pump end face are 459.24 ℃ and 535.78 ℃,respectively. The mass ratio of neodymium ion in the crystal is 1.0%. The size of microchip is Φ20 mm×1 mm. The pump power is 60 W. The absorption coefficient of Nd∶YAG crystal is 910 m-1 . The super-Gaussian beam order is 3 and the pump light spot radius is 800 mm. The analysis results are helpful to the design of LD end-pumped solid-state heat capacity lasers resonator.