The impact force generated by the vessel berthing terminal is an important load for the terminal design，and the rational determination of its value is a very important.Because of many factors，in international research field there are some calculation formulas for the impact force，but there exists some differences between them，especially on the impact force of large oil tankers berthing at the open sea terminal.The paper analyzes the calculation formulas of several representative theories in the domestic and international research，and makes a comparative analysis，which indicates that there are some differences between the domestic code and international research or the physical model test results for calculation of vessel impact force.In order to determine the impact force of the large oil tankers berthing at the open sea terminals，the paper puts forward suggestions for improvement of the code formula.