Abstract: For the purpose of optimizing the flow-dividing structure,the effect of diameter of flow-dividing holes on the performance of liquid-jet hammer and the average flow velocity at the cross-section of the nozzle of the fluidic element is investigated by means of CFD (computational fluid dynamics) dynamic analysis,and the simulation results are verified by experiments.It is shown that under conditions of different diameters of flow-dividing holes the maximum relative error between the calculated blow energy and the tested is not greater than 10%,and the maximum relative error between the calculated blow frequency and the tested is less than 11.5%.The results show that blow energy decreases approximately in the form of parabola and blow frequency and the average flow velocity at the cross-section of the nozzle of the fluidic element decrease approximately linearly as the diameter of flow-dividing holes increases.This investigation solves the problem that there is no method for calculating at the designing stage the performance parameters of liquid-jet hammer and the average flow velocity at the cross-section of the nozzle of the fluidic element when flow-dividing mechanism is involved,which can provide a reference for optimizing the internal flow-dividing mechanism in liquid-jet hammers designed for oil and gas drilling.