RNG k ε turbulence model is adopted to simulate the cavitating flow of annular groove within relief valve，and the influence of structural parameters of annular groove on cavititaing flow field is analyzed. The analysis results show that performances of resistive cavitations increase with the rising of structural parameter θ when structural parameters R1and R2 are the optimal values. According to numerical simulation data of annular groove’s structural parameters，the surrogate models is obtained via the kriging calculated method，i.e. the objective function is the maximum gas volume fraction，the correlation function is the Guass function and constant regression model is applied to the likelihood function of surrogate models. The surrogate function is optimized by the improved PSO algorithm，and resistive caviatation property of the optimized structural parameters has higher efficiency compared with other ones.