Abstract: Submarine oil pipelines are usually buried in the seabed silt. With the change of seabed over the time, the submarine pipelines are partially suspended and exposed to sea water directly. The cathodic protection and corrosion condition of submarine pipelines in sea water are different from those in sea mud. In this paper, the mathematical model was established and the boundary conditions were determined. Then, the cathodic protection situations of submarine pipelines in sea water and sea mud were numerically simulated and analyzed respectively using the finite element method. The following results were obtained. First, the potential change of submarine pipelines is smaller and more stable in the sea mud. Second, the corrosion rates of submarine pipelines under the sacrificial anode cathodic protection are 0.064 μm/a in sea water and 0.053 μm/a in sea mud, which are much lower than the average corrosion rate of steel structure without sacrificial protection in the sea mud area. And third, the service life of sacrificial anode is 4.58 years in sea water and 13.3 years in sea mud. The results provide the theoretical reference for the design and security management of the corrosion control of submarine pipelines.