Abstract: It is the most complicated problem in the collision avoidance of ship that multiple ships encounter with each other at sea, and also is one of the difficult points for ship's automatic collision avoidance. In this paper, the strategy about ship intelligent collision avoidance is firstly stated in brief. The compartmentalizing principle and the classification for the situations of multi-ship encountering with each other is discussed then. The method for building and optimizing the intelligent decision of multi-ship anti-collision in open sea area is talked over emphatically at last.