The existing three types of determination methods of offshore wind power monopile foundation are summarized, which are limit equilibrium method, p-y curve method and qualitative method, and the difference in the horizontal ultimate bearing capacity calculated by different methods is studied combined with the test cases. The results show that the results obtained by different methods are quite different, and the maximum gap can reach 38.84%. Since there is no uniform method and the results obtained by different methods vary greatly, further research is needed to determine the horizontal ultimate bearing capacity of the monopile foundation.