The hydrothermal vent system will produces a large number of chemical plumes during the eruption process. Relevant characteristics of chemical plumes can be used to navigate underwater robots to achieve the source positioning. This paper establishes the source distribution probability model and obtains the source distribution probability graph by analyzing the motion law of chemical plumes in water. According to the actual water flow environment in the actual searching, the artificial potential field method is improved and the force direction of underwater robots during the motion is obtained through the calculation. Then, the direction of motion of underwater robots is continuously adjusted combined with the source probability distribution graph, finally achieving the tracking and positioning of chemical plumes. At the same time, the overall process of the tracking and positioning of chemical plumes by underwater robots is studied. The main process includes reaching the primary area, starting the first search, discovering chemical plumes, tracing chemical plumes, rediscovery and searching, and source positioning. It provides a reference for the tracking and positioning of chemical plumes by underwater robots.