Abstract: The sacrificial anode cathodic protection system of an in-service subsea oil pipeline was used as the application object. Indoor experiments combined with numerical simulation methods, as well as methods such as subsea pipeline potential measurement and sacrificial anode sampling testing, were used to obtain the protection potential level of the subsea pipeline and to estimate the sacrificial anode life. The results indicate that there was a slight deviation between the electrochemical behavior of the sacrificial anode in the sea area and the initial design value. Combined with the numerical simulation results, the sacrificial anode life could meet the initial design requirements (35 a) and the protection potential of the submarine pipeline met the standard during the life period. The pipeline was in effective protection. The combination of numerical simulation methods and practical detection had good consistency and complementarity in evaluating the cathodic protection status of sacrificial anodes for submarine pipelines.