This study examined the relationships between learning interest, flow, and creativity among high school students. As a state of interest, flow served as a mediating variable on the route from interest to creativity. The participants included high school students from a city in eastern China. The software of "Process" was adopted to analyze the effects of learning interest on creativity by flow. The results revealed that the dimensions of enjoyment and clear goal of flow served as significant mediators and that the mediating effect of enjoyment was significantly larger than that of clear goal. The model presented a consolidated picture on the relationships among the three variables and connected the studies of interest and flow.