There are so many serious problems of traditional dry sand blasting,such as dust pollution, uneven results of the surface sandblasting processing,low productivity and so on. A new type of wet sand blasting machine was designed based on PLC. Through erosion effect of high speed grinding abrasive liquid jet, it was used for surface strengthening, improving stress process requirements with compressed air as the driving force.The main parameters of the wet sandblasting machine were optimized by CFD simulation. The nonuniformity problem was solved by the improvement of processing scheme, and automatic control was realized by PLC controller. The test shows that roughness meets the requirements of the original production technology, surface residual stress distribution is uniform, significantly superior to the traditional dry sand blasting effect after wet sand blasting. Wet sand blasting effectively eliminates the traditional dry sanding the problems of dust pollution and so on. Because of the simple and convenient operation, stable and reliable running, convenient operation and the advantages of the application efficiency, it can be widely applied in the metal workpiece surface strengthening and modification,and has higher application promotion value.