Based on transient heat conduction equation, pulse Gaussian beam dual-end pumped Tm:YAG rod time-varying temperature field analytical expression and the time-varying thermal focal length are obtained by the integral transform method. The effects of pumping power, repetition frequency and duty ratio on pulse laser diode dual-end pumped Tm:YAG rod axial transient temperature distribution and the time-varying thermal focal length are quantitatively analysed. Simulation results show that with the increase of pulse number, the temperature distribution and the thermal focal length of Tm:YAG crystal rod appear jagged and eventually get to the periodic distributions. As the increase of pumping power, repetition rate and duty ratio, the whole temperature of Tm:YAG crystal rod increases and the temperature difference between the Tm:YAG rod on both ends of the center and the axis center of rod becomes larger, while the time-varying thermal focal length gradually becomes shorter and the fluctuation range is smaller. The results provide theoretical basis for the further study of heating compensation and cavity design.