The Kaohsiung harbor is the most important harbor in Taiwan. Two thirds of Taiwan’s international commerce goods are handled in this harbor. The future development of the harbor is influenced by many factors, namely port operational efficiency, port safety, weather condition, national, economic growth rate, and political stability. Although operational efficiency is important; however safety is even more important than operational efficiency. From this point of view, Kaohsiung harbor will soon launch its vessel traffic management system (VTS). Piloting service is one of the crucial elements in the development of a port’s VTS. This article analyzes pilot’sservice behaviour in the Kaohsiung harbor and proposes appropriate pilots management regulations in the future VTS mechanism. In the paper, we applying principle component analysis and three key factors effects pilot's service behaviour under VTS regulations are found, namely, weather condition, sea condition and pilot experience. Three principle components accounted for over 62.247 percent of the data set. This result justified our efforts to represent the tongue shapes with the three basis factors the weather condition, pilot experience condition and sea condition. Therefore future VTS’s pilot regulations should take the abovementioned three factors into consideration. Key worlds: Pilot, Kaohsiung harbor, Principle component analysis