Diet management has become a common concern in daily life. Most of the current related designs provide accurate calorie estimates and personalized diet recommendations, which does not touch the core of management – how to make this behavior active and sustainable. This study introduces the concept of Positive Design, constructs a three-step design path which is applied in practice, aiming to give long-term happiness to diet management and promote users’ active adherence. The vital step is to invite target users and designers to join in collaborative work, identify and filter eight conflict dilemmas which are worthy of study. Positive design is a new theoretical perspective based on positive psychology. The final scheme produced in this paper aims to explore the application of this method in diet management design, and also provide a certain reference for subsequent research.