Aiming at the situation that there is still no applicable calculation method for different types and total anchorage number of seaport，and based on the investigation of the domestic coastal port use and management departments，and existing standards and relevant data are collected，this paper mainly analyzes the scope of application and existing problems and limits of different existing calculation methods. And the calculation methods for different types of anchorage numbers are put forward，such as piloting，anchorage waiting for tidal window，lying anchorage，emergency anchorage，inspection and quarantine anchorage，lighterage anchorage，and sheltered anchorage. In consideration of common usage among those types of anchorages and that ships would be cleared out before gale weather，it should be better to choose a larger value between sheltered anchorage numbers and the other anchorage numbers. The calculation results are testified appropriate for practical cases，which could provide a reference for the calculation of the number of anchorages of seaport.