Genetic algorithm is applied to solving the problem of collision avoidance in ship navigation. When utilizing this method, the first step is to code the solution of problems as a finite-length string. For the studied subject, in the conventional coding, the position (longitude and latitude) of the ship is chosen just as genes of a chromosome. This was not especially good for checking the experimental values. In this paper, a new way of coding is proposed, where a single gene is constructed with the position and speed of the ship, as well as the factors of tide, wind, and wave. Then it is verified with both an automatic collision avoidance simulation system developed in the VC++ language and a real ship. The experimental results show that this new coding is a more effective way to search for the optimum and safe path.