Combined with the concept of flat and the concept of full life cycle, the whole life cycle of cocktail packaging was proposed. Through the analysis of typical design cases, the whole life cycle of flat cocktail packaging was explained, and a complete design process of flat cocktail packaging was constructed. Taking the design of self-created cocktail brand as an example, the flat design process was verified experimentally. The results show that the flat design process is helpful for designers to judge and design flat packaging in the whole life cycle.