This paper explores the application and influence of human-computer interaction behaviours in the visual design of smartphone APP interfaces. This paper firstly analyses the user's behavioural characteristics, interaction mode and optimization of the interaction process, and points out that the interface design should be closely integrated with the user's needs. Then the article puts forward the principles of smartphone app interface visual design, which provides a guiding framework for designers. In elaborating the design elements, the importance of colour, icon and text in interface design is emphasized, and the corresponding design principles and methods are proposed. The article concludes with a summary of the research results pointing out the problems and shortcomings, and looking forward to the future development trends and directions. This article aims to improve the user experience rate and interaction efficiency of smartphone APP interface design, and provide useful references for research and practice in related fields.