In order to investigate the characteristics of vessel traffic flow extensively and accurately, a field method was introduced to analyze the vessel traffic flow. Based on the ideal grid arrangement, this process used the AIS data of vessel traffic flow as samples and applied Delaunay subdivision for trigonometric interpolation to obtain the distribution diagram of vessel traffic flow field. The comparison with the actual traffic flow shows that the form of field can well characterize the distribution of vessel traffic flow and the safe state of navigation area. Utilizing the analysis results of vessel traffic flow field, the effectiveness of safety prewarning of ship navigation and maritime safety supervision can be improved.