Abstract: In two-phase fluid medium of sulfate acid solution,corrosion wear properties of N80 and P110 oil well tube steels were investigated with a self-assembly wearing device,and synergistic rate and interactive ratio of corrosion wear for two steels were comparatively analyzed respectively, and choice of service condition of two steels was discussed.Results showed that corrosion rate,wear rate and synergistic rate of N80 steel are a little higher than that of P110 steel in the medium,and vary with either concentration or rotary speed of the medium.Synergistic rates increase with increase of either rotary speed or concentration of two-phase medium in the corrosion wear process,but interactive ratios vary immonotously and can reach the maximum under a little high concentration and low rotary speed of the medium.It is more reasonable that N80 steel is chosen for the condition of both high concentration and low rotary speed,and that P110 steel is chosen for the condition of both low concentration and high rotary speed.