Based on standard k-ε model of Fluent, the 3-D numerical simulation of cavitations-impinging stream reactor was studied. The main flow law in the reactor was obtained, and its velocity and pressure fields were analyzed. The results showed that the parameters of the flow field were completely symmetrical by the impinging surface; isobar concentrate in the impinging area which indicated that pressure fluctuations in this region is stronger, it plays an active role on the promotion of flow group micro-mixing. The laws of parameters influence on impinging phenomenon were revealed by analysis the results with different parameters. The basic data and theoretical bases are provided for the optimized and improved design of impinging streams reactor.