To calculate the range of motion of navigation marks in the deep water，a theoretical model of navigation marks’mooring system is established and the formulas of navigation marks’range of motion in different mooring states are derived according to the cater nary equation.For the excessive range of motion of navigation mark in the deepwater environments，the two-point mooring mode of navigation marks is proposed，which reduces greatly the navigation marks’range of motion.This paper calculates various parameters of navigation marks in different water depths combining an example.The results meet the accuracy requirements of the project，and it indicates that the method has certain reference value in the engineering.