Abstract: In this paper, the surface of as-cast nickel aluminum bronze (NAB) was modified by submerged friction stir processing (SFSP) technology in order to further improve the cavitation resistance of it. The microstructure and mechanical properties of the as-cast and SFSP NAB alloys were observed and estimated. The cavitation erosion behaviors of two NAB alloys in distilled water and artificial seawater were compared and discussed, and the relationship between microstructure and cavitation mechanism was analyzed. The results show that after SFSP, the microstructure of the NAB is refined and all phases are uniformly distributed.The average microhardness in the center of the processing area is about 400 HV, which is twice that of the as-cast sample. In both test solutions, compared with as-cast NAB, the cumulative cavitation erosion mass loss of SFSP NAB was lower. After 18 hours of cavitation erosion, the mass loss of SFSP NAB in distilled water and artificial seawater is 2.55 mg and 4.85 mg respectively, which is about 50% and 44% of the mass loss of as-cast NAB. It has better cavitation erosion resistance. Grain refinement and small grain size κ Phase dispersion strengthening is the main reason to improve the cavitation resistance of as-cast NAB.