The study on the whole life cycle cost of floating offshore wind turbine is insufficient in China. This paper proposes a method to evaluate the whole life cycle cost segmentation of floating offshore wind turbine. The six stages are: pre-investigation stage, design and development stage, manufacturing stage, installation stage, operation and maintenance stage and dismantling stage. Each of these stage costs can be subdivided into different sub-costs to obtain key variables of operating life cycle costs. In addition, consider the percentage of cost of semi-submersible floating platform analysis, the percentage of cost at each stage of the life cycle, and the percentage of sub-costs, so as to obtain the most important cost and minimize it to improve the economics of floating offshore wind turbine. The research shows that controlling manufacturing cost and installation cost is the key factor to reduce the floating offshore wind turbine whole life cycle cost.