In order to reduce the thermal effect of Nd:YAG ceramic laser side-pumped by pulsed laser diode bar, improve the stability of resonator and improve the performance of laser, the temperature rise and thermal deformation field generated by pulsed laser diode bar side-pumped laser ceramic were studied analytically by using the heat conduction theory. Based on the analysis of the working state of the laser ceramic side-pumped by pulsed laser diode bar, a thermal analysis model suitable to the actual situation was established, and the general analytical expressions of the temperature field and thermal deformation field in the pumping period and the pumping interval were obtained by solving the Poisson equation of heat conduction. The three-dimensional temperature field distribution of Nd:YAG ceramics pumped by the side of pulsed diode bar, the temperature field distribution in the process of repeated pulse pumping, and the influence of different pumping parameters on the temperature field were analyzed quantitatively. The thermal shape variables on the pump surface were analyzed quantitatively when the thermal dynamic equilibrium was reached. Calculation results show that: when the pump power is 60 W, repetition frequency is 100 Hz, beam waist radius is 150 μm, neodymium ions doped mass fraction is 1.0%, the Nd:YAG ceramic pump surface produces temperature rise of 29.6 ℃, pump surface and smooth surface produce 0.95 μm and 0.99 μm hot shape variables. The analytical method of temperature field of laser ceramics solves the problem of low accuracy caused by numerical analysis method, and it can also be applied to other thermal problems of laser system, which provides a theoretical basis for reducing the thermal problems in laser system.