The flow line method occupies a very important position in cartography. It is able to synthetically express the direction of actions, the movement routes, the increase or decrease of the number, and the quality change of spatial entities or phenomena. Flow line method is a difficult subject in computer graphics, which has not been satisfactorily resolved. The traditional fixed-line method is linear symbols. However, there are many limitations in the practical application of linear symbols. To solve this problem, the author proposed the correlation algorithm of curve line symbol and developed a WEB-side system for the moving line method with respect to adaptive cartography, which is based on the open source software MapServer. This article is mainly consisted of three parts: the flow line symbolic algorithm, the database management system, and the map display system. The flow line symbolic algorithm was discussed based on the map display system developed by the Visual Studio 2010 platform, which was consisted of curve symbolic algorithm, obstacles avoiding algorithm, and confluence and difference algorithm. The database management system was established based on the shape file format of spatial data and Oracle environment attribute data. The map display system was used for WEB-side adaptive map display and other interactive functions. In the article, the floating population data was used as an example to verify and describe the system functions of the thematic map display, the hazard avoidance, and the confluence and difference calculations. According to the thematic map, we could analyze the floating population data easily, accurately, and intuitively. This provides great assistances in data supporting and decision making for other studies of floating population and related disciplines. In addition to the floating population, the system is also adapted to the data presentation and analysis of economic development, social factors, military combat, natural phenomena, and so on. It can accomplish the functions including curve symbol drawing, obstacle avoidance, and confluence and difference calculations. That is, the flow line symbol algorithm is a great help for the visualization of temporal expression data, and it has broad application prospects.