In order to study the influence of the nozzle outlet flow path shape on the erosion effect of the cavitation water jet, based on the self-developed submerged jet erosion experiment device, an experimental study has been conducted on the erosion of ceramic brick specimens by cavitation water jets of the self-designed ordinary nozzle, gradual contraction-sudden expansion nozzle and gradual contraction-gradual expansion nozzle, thus obtaining the law of the erosion depth, erosion damage area and the quality of iron powder filled with erosion with the target distance and back pressure. The results show that the gradual contraction-sudden expansion nozzle and gradual contraction-gradual expansion nozzle are characterized with a significantly better jet erosion capacity than that of the ordinary nozzle; the cavitation water jet erosion ability of gradual contraction-sudden expansion nozzle and gradual contraction-gradual expansion nozzle has the best back pressure value；the gradual contraction-gradual expansion nozzle has longer optimum standoff and the gradual contraction-sudden expansion nozzle has stranger ability of resisting back-pressure.