As thyristor valve is the core equipment of quench protection system of large fusion device, the design and optimization of its snubber circuit parameters are related to the safety and reliability of the valve and even the whole quench protection system. So far, most of the design and optimization of snubber circuit parameters are based on DC steady-state conditions. However, there are few literatures on parameter optimization under impulse conditions. In this paper, the buffer circuit parameters of thyristor valve are designed and optimized under the pulse condition of superconducting magnet quench protection system. Based on the exponential model of thyristor reverse recovery current, the current mathematical model at the turn-off time is established. The relationship between the key parameters is obtained through experiments, and the reverse recovery model of thyristor current is established in Matlab according to thyristor performance and system requirements. Considering the performance requirements such as current drop rate at turn-off time, peak reverse recovery voltage and the cost, a parameter design and optimization method of thyristor snubber circuit under pulse condition is proposed. The model of quench protection system is built in Matlab, the simulation results show that compared with the original parameters, the optimal parameters reduce 11% of the peak reverse recovery voltage and 43% of the peak reverse recovery voltage change rate. At the same time, the manufacturing cost of the circuit is reduced to 1/7 of the original one.