Abstract: This thesis is reference for the economic losses assessment method and thought of natural disasters. Based on the influence objects of Ulva prolifera, with scientific, comprehensive, operability and practicability for the principle, divide the disaster losses into several parts as mariculture, coastal tourism, Marine traffic, industrial emergency management and marine ecology. The disaster losses system of investigation and assessment method of Ulva prolifera has been established, providing technical support for investigation and assessment of Ulva prolifera losses of operational application.