For the coupled effects of the fluid flow,convective-diffusive and transient thermal conduction happened in the process of pumping and cooling,a flow-thermal-solid interaction model for calculating the temperature distribution in the laser crystal has been established based on the coupled analysis of multi-physics fields. The transient temperature distribution of a laser slab pumped by high-power repetitive pulses is obtained by using the finite element method. The proposed method precludes the influence of the inaccurate film coefficient of the cooling water on the calculation results. Therefore,for the purpose of reducing the thermal effects in the laser crystals,it provides a new effective way to assess and improve the cooling process.