Abstract:  The environmental force acting on the South China Sea semi-submersible platform is analyzed and studied through the example of a semi-submersible drilling platform with anchor location. For the heading determination of a platform operating in the internal wave flow waters, it is very important to consider the influence of wave function on the platform positioning. Through calculation and analysis, it is definitely concluded that the principle for determining platform heading is to minimize the environmental force acting on the platform. The heading of the platform should be set to the direction of incoming waves, so as to reduce the current force on the platform, and to ensure stable and safe operation of positioning. For operations in the South China Sea where internal waves are frequently found, we need reasonable standards and guidelines to avoid the drift and damage of the platform caused by the internal waves and to ensure the safety of deepwater operation.