The work aims to analyze the categories of materials, users and conditions of use of children's outdoor facility products, summarize the expression dimensions of material immateriality in product design, and provide a new perspective of product material selection from the immaterial perspective. The research status of materials in children's products was summarized by literature review. Based on the actual product cases obtained from research, the application of materials in the products was counted. In combination with chart analysis and case study, the expression of material immateriality in the product image dimension was discussed from the physiological, psychological, and cognitive dimensions of children. The expression of material immateriality in the product meaning dimension was discussed from the use place, design theme, and experience dimension. The expression of material immateriality in product shape and structure was discussed from from the dimension of "type" and "structure" of material. The immaterial correlation between material and product was constructed. The immateriality of materials can be a new material selection factor for children's outdoor facility product. In terms of image expression, it revolves around the users themselves, reflecting the expression of the "material use" level of the product; in terms of meaning expression, it is related to the theme, context, experience, and other factors of the product, reflecting the expression of the "material context" level; in terms of shape and structure expression, it is the extension and expansion of the materiality of the material, reflecting the expression of the "material structure" level.