Large-tonnage ships or ships with less navigation quantity are generally considered to enter or leave the port by tide and arrange anchorage for waiting tidal due to the lack of port coastline. Aiming at the problem that there is no suitable calculation method of anchorage number for waiting tidal window，we propose the factors affecting anchorage number for waiting tidal window including ships arrival regular pattern，tidal characteristics and channel management based on investigations，existing standards and by theoretical method analysis，obtain a calculation method of anchorage number for waiting tidal window by analysis of influencing factors，and verify the method by the actual example. The results show that the calculation method is reasonable and feasible，and can provide the references for anchorage planning and design.