Abstract: Based on the existing losses assessment methods for red tide disasters proposed by the predecessors and the hazard characteristics of red tide disasters, economic loss assessment index of red tide disasters is put forward based on the actual needs and the operational data that can be got in the operational work.The losses assessment system for red tide disasters is based on ArcGIS Engine and Visual C#, established to realize functions of data input and management, GIS data detection query, loss evaluation model calculation, thematic maps production and output, and achieve visualization of assessment results.The results of the assessment include the losses assessment of marine aquaculture industry, the losses assessment of coastal tourism, the assessment of the cost of emergency monitoring and the assessment of the cost of disposal of red tides.It also plays an important role in the local post-disaster rescue and economic losses assessment and also provides the scientific basis for the managers' decision-making.