The progresses and theoretical methodology of computer modeling of cathodic protection using the boundary element method (BEM) are outlined. To test the effectiveness and accuracy of BEM numerical modeling of cathodic protection for offshore structures, a miniature model offshore jacket with a sacrificial anode was built and put in a test pool full of seawater. Cathodic protection potentials on different positions were measured and compared with the values obtained from computer modeling. The results show good agreement between measured value and numerical simulated value. The factors that led to discrepancy in the two groups of data were discussed.