Along with world shipping economy continues to push forward and the progress and development of science and technology, the number and size of large vessels are enlarging continually. The largest vessel in the world has reached five or six hundred thousand dwt, especially very large oil tankers, bulk carriers and large container vessels. The safe berthing becomes a pressing concern of the pilot and the captain. The workload of harbor is heavier and heavier. However, there is no advanced system assisting pilots to guide large vessels to enter and leave port safely. As a result of that, the pilots are faced with a lot of pressure. In order to improve the security and efficiency of the berthing process of large vessels, lighten the heavy burden of the pilots and decrease the possibility of the accident during the process of pilotage, this paper introduced the berthing system's history and development, analyzed large ships' berthing process, researched the technologies of the DGPS combination positioning, WIFI and AIS, built up the ship-based plane coordinate system, shaped the large vessels' berthing mathematical model based on the technology of DGPS, provided the means of calculating the dynamic and static parameters and then gave the structure of the whole system. In this ship-based plane coordinate system the model can accurately calculate the berthing ship's dynamic parameters, such as the exact position of the vessel, the distance between the vessel and the pier, the relative velocity between the bow and the pier, etc. With the help of the combination technologies of AIS, WIFI and two-point positioning technology DGPS, the large vessels' berthing system which has passed the test of reliability and availability is finally designed. In the test, it can be shown that this system could provide high-precision information such as the latitude and longitude, movement speed, the distance to the wharf line and other auxiliary information which the pilot need in the progress of pilotage. The accuracy of the position can be within 60 cm, and the speed accuracy can be within 5 m/s, which provides more intuitive, convenient, and fast sailing navigation for the pilot and then effectively improves the security and efficiency of large vessel's berthing progress.