In my study, I use ontology to make the wind turbines related knowledge to be more accurate description, so that the manufacturers can find the information they need more easily. The establishment of related inferences and inductive knowledge between objects have made the wind turbine information easier to understand and easier to get stated. To develop an offshore wind turbine decision support system for helping the manufacturers choosing wind turbine, I used ontology as the basic of my system including the wind turbine information and international specifications. By the procedures of visit the experts and manufacturers, I design a set of system providing Taiwan wind farm classes judgment, annual generation capacity calculation and the weighting of experts model. This study is to help the wind farm manufacturers to choose the wind turbine faster and easier, also help to promote the wind power industry of Taiwan.