Based on the Reynolds time-averaged Navier-Stokes equations and the standard k-ε model, the law-of-the-wall modified for wall roughness effects, the performance and mechanics characteristic of an axial-flow pump with different surface roughness were simulated. The variation trend of the momentum, head and efficiency with the wall roughness was obtained. The influences of wall roughness on head, momentum and efficiency were approached. The efficiency potential of commercial axial pumps can be drawn. A mechanical treatment or coating to smoothen the surface can considerably increase the efficiency and the head. The research results are of great significance to understand the effects of roughness on the performance of axial-flow pump and to improve the efficiency of the axial-flow pump.