Abstract: It is important to assess quantitatively the direct losses caused by marine environmental pollution for damage compensation and administrative penalty.But due to different responsibilities and perspectives, there is still no consistent assessment contents and quantitative methods on direct losses in China.Considering both human and marine ecosystem, the pollution damages are analyzed and categorized comprehensively.It reveals clearly the category and scope of pollution damages, especially the connection and distinction between human activities damage and marine ecosystem damage caused by pollution.Furthermore, according to the popular theory and laws, the direct losses of all kinds of damages are identified.And then, based on the principle of science and quantization, the assessment index system is proposed, including the four losses of personal injury, property damage, marine ecological damage and administrative affairs expenditure, which are further divided into the 11 indexes of physical injury, mental injury, loss of aquatic products, loss of fixed assets, loss of current assets, additional cost for protecting assets, loss of profit during recovery, cost of marine ecological restoration, loss of ecosystem services during recovery, cost of emergency disposal, cost of investigation and evaluation.The research results could give support to the quantitative assessment of marine environmental pollution damage, and make damage claim and administrative punishment more quantitative and scientific in china.