Excellent product appearance design can better attract consumers, stimulate their purchasing desire, and provide users with a better user experience. Poor product appearance design can deter users and cause them to miss the opportunity to purchase. The appearance design of handheld beauty devices has a very important influence on the promotion and application of the products. Therefore, the appearance optimization of handheld beauty devices plays a very important role in the competitiveness of the product, and is even directly related to the survival and development of the enterprise. Since users’ aesthetics are subjective and diverse, when conducting the optimization design of product appearance, it is necessary to accurately obtain the needs of different users, acquire the emotional data of users towards the product, and utilize these emotional data to optimize the product appearance. Combined with Kansei Engineering, the designed products have stronger advantages. This paper explores a method for optimizing the appearance optimization design of handheld beauty devices by using the Stable Diffusion model and the fuzzy evaluation method.