Through the comparison of three methods for the grid interconnection of offshore wind power,this paper pointed out the application prospects of fractional frequency transmission system (FFTS) in large-scale offshore wind power integration.Besides,this paper introduced the structure of fractional wind power system and the choice of inverter and showed the excellent performance of modular multilevel converter (M³C) as a new generation inverter.Moreover,this paper analyzed the influence of low frequency on the critical machines used in fractional offshore wind power system,which furtherly shows the feasibility,economical advantages and technological advantages of the fractional offshore wind power system.Finally,some economical and technological problems remaining unsolved of the fractional offshore wind power system were pointed out,which indicated the direction for further study.