From the perspective of science of design, this paper aims to explore the design method of children's emotional companion toys.Through social research combined with theoretical analysis, the external and internal factors of the "things" in the emotional companion toys for left-behind children aged 7-12 in the city were refined, and a reasonable design model and evaluation system for children's emotional companion toys were established; proper use of case analysis and in combination with the design cases and practice of children's emotional companion toy, this paper aims to verify the application value of science of design in the actual design. By exploring the design path of children's emotional companion toys, combined with Combot - a children's emotional companion toy with emotional companionship and entertaining functions as a practical case, it proves that the design method of children's emotional companion toy based on design affair is effective and feasible which can effectively guide the design of children's toys, meet the emotional needs of both parents and children, and promote the healthy growth of children.