LNG fuel is considered as an ideal engine fuel in future because of its excellent environmental performance, low price and strong safety. The high energy consumption and pollution emission of the fuel diesel engine on the fishing vessels have become one of the main causes of the offshore environmental pollution. In order to promote the energy conservation and emission reduction for the fishing vessels, LNG fuel transformation for the existing fishing vessels becomes a reasonable answer. It analyzes the technical scheme and the economy of LNG power modification for a 38m beam trawler, as well as the feasibility of the power modification. It also presents the main issues and its countermeasures of the LNG power modification for the fishing vessels.