The scale yield function has a great influence on the study of cross-border logistics platform building and rural agricultural products e-commerce selling. This paper analyzes the main factors affecting the effect of cross-border logistics platform construction through factor analysis. Among them, platform content construction, platform service level, platform user management, platform supply chain construction, and platform development potential are the most important factors of cross-border logistics platform construction. The linear combination is used to construct a cross-border logistics platform integrating content, service, management, supply, and development. The regression method is applied to calculate the factor scores, and the assumed return to scale is applied to calculate the relevant data after the construction of the cross-border logistics platform. Seeking the maximum scale return rate is greater than 80%, the return is higher. The experiment proves that the construction of a cross-border logistics platform can expand the rural agricultural products e-commerce sales market from mainly China to parallel sales in China and European and American countries, etc., and improve the scale gain. Relying on the construction of a cross-border logistics platform, the total sales of rural agricultural products and e-commerce sales in foreign countries increased by more than 10 million, and the revenue was higher than 4.5 times of previous years. Thus, the construction of a cross-border logistics platform is conducive to expanding the market of rural agricultural products e-commerce sales and increasing rural agricultural products e-commerce sales.