Weight-loss tests of three kinds of steel were conducted in various sea-bottom sediments. After analysis of sea-bottom sediment investigation results and of data on regional corrosion factors the authors propose a two-factor method for evaluating sea-bottom sediment corrosion. Two main factors affecting corrosion are sediment type and the number of sulfuric reduction bacteria. If A°is corrosion related to sediment type, B° the corrosion related to sulfuric reduction bacteria, then the total corrosion can be expressed as C°=A°+B°.