The invention relates to a construction method applied to split installation of offshore wind power generators. A wind power generator is located on a bearing platform of a fan foundation and comprises a tower frame and a fan located at the upper part of the tower frame. An auxiliary platform is used for lifting the wind power generator on the fan foundation, so that the split installation of the wind power generator is achieved. Through the construction method, the auxiliary platform is used for achieving split installation of the fan; the influence of the wind wave on the installation construction of the fan is effectively reduced; the installation efficiency is improved.