Mooring force is an important factor in wharf structure design and mooring bollards selection. The calculation methods of ship mooring force are different between different codes. Regarding the differences in current force calculation，this paper selects four wharf structural design specifications for comparison，namely JTS of China，ROM of Spain，OCIMF Guide and BS 6349 of Britain，and takes a 300，000-ton tanker as an example. The results show that：1）there are some differences in the calculation formula，relative water depth ratio，design current velocity and adaptive range of the current force on ships；2）The current force of the 300，000-ton tanker calculated by ROM is the largest，while the BS 6349 result is the smallest. The conclusion can be used as references for similar engineering design.