Reasonable bit hydraulic structure can avoid mud bag phenomenon and improve drilling efficiency.In order to improve the hydraulic structure of bionic PDC bit,four different hydraulic structure schemes were numerically calculated based on κ-ε turbulence model and discrete phase model.The best scheme was the combination of nozzle and auxiliary nozzle.In order to determine the optimal structural parameters under this scheme,a mathematical model with nozzle diameter x1 ,auxiliary nozzle diameter x2,radial distance from nozzle to drill center x3,maximum velocity of sampling point D and average velocity of sampling point E as objective functions was established by response surface method.Based on regression analysis,the hydraulic structure of drill bit was optimized.The optimal parameters were obtained as follows:nozzle diameter 16.36 mm,auxiliary nozzle diameter 8 mm,radial distance from nozzle to drill center 63.85 mm,and the hydraulic structure under this parameter was numerically calculated.The results show that the optimized hydraulic structure of the drill bit not only reduces the number of bottom hole velocity fluctuations,but also significantly improves the overall velocity, solves the original eddy current phenomenon,enhances the rock carrying performance of the drilling fluid and reducing the particle concentration.