Downhole tools are one of the critical factors to guarantee the successful application of hydra-jet fracturing technology which is a new stimulation method with perforatingfracturing and hydraulic sealing.Some donwhole tools are cut open and the severe wear areas around the nozzle inlets inside them and on their surfaces are analyzed.In order to investigate the reason for the inside wearthe flow field inside the tools are numerically simulated.The results show that the splashback abrasive jet will erode the surface around the nozzles of the tool.For surface wear at different positions along the tool axisit will be more serious at the downstream than that at the upstream.At the same timeif the formation is loosethe abrasive jet with a high velocity will splash into formation and return from other existed perforationsresulting in extra wear at the surface relatively far from the nozzles or even the tubing’s surface.For the inside of the toolsthe wear at the upper area around the upstream nozzle inlet and lower area around the downstream nozzle inlet will be more obvious than that of other positions.The numerical simulation results explain this phenomenon clearly.The research provides reference for improving the downhole tool’s structure and its life.