Abstract: It is difficult to determine whether the offshore F-class gas turbine power plant adopts Once-through cooling water system or circulating cooling water system by qualitative method. Taking an offshore F-class gas turbine power plant as an example, the technical and economic comparison is made between the Once-through cooling water system and circulating cooling water system with mechanical ventilation cooling tower. The results show that seawater oncethrough cooling water system has the advantages of small weather influence, low condenser back pressure, high power generation efficiency, low noise in the plant area, and less consumption of fresh water resources, and can be used as the recommended solution for circulating cooling water supply of this project.