Abstract: With the increasing popularity of online shopping, the E-commerce supply chain has gradually become a mainstream consumer channel, which has led the E-commerce platform to become channel leaders. In E-commerce supply chain, consumers usually perceive products by browsing images and text descriptions, and product quality is gradually becoming a key constraint on product sales. Therefore, considering the impact of product quality, decision-making models of E-commerce supply chain are constructed, including decentralized decision-making without considering concerns, decentralized decision-making of considering platform's altruistic preference concerns and centralized decision-making.
In these three models, the manufacturer's profit function is π_m=(p-ρ-c) q-hμ²/2-f. The profit function of the E-commerce platform is π_e=ρq-ks²/2+f, and the utility function is U_e=π_e+θπ_m.
In these functions, p is unit sales price of products; c is unit production cost; ρ is the unit product commission charged by the E-commerce platform to the manufacturer (assuming that ρ<p-c); μ is quality level of product; s is the platform's service level provided to selling; f is the technical service fee paid by the manufacturer to the e-commerce platform; q=α-βp+δμ+γs is market amount.
Then, the optimal decisions of three models are solved and comparatively analyzed to discuss the influence of platform's altruistic preference concerns on supply chain decisions. Then, the influence of altruistic preferences on E-commerce platforms is explained with actual cases. Finally, numerical examples are used to verify the conclusions.
Research shows that:(1) Consumers' emphasis on product quality can increase the profits of the manufacturer, the E-commerce platform and supply chain system. (2) The platform's preference concerns under decentralized decision-making can improve the manufacturer' profit, while harm the platform's profit. The supply chain system profit first increases and then decreases due to the platform's preference concerns. Moreover, when the E-commerce platform has an altruistic preference, the relationship between product prices under decentralized and centralized decision making is uncertain, which is different from the conclusion that "prices are lowest under centralized decision making" in traditional supply chains. (3) Service level, sales price and product quality increase with the increase of altruistic preferences, and the rate of increase grows faster. But there is still a large gap between the optimal decisions of decentralized decision-making and centralized decision-making. (4) The altruistic preference behavior of E-commerce platforms is mainly manifested in the fact that E-commerce platforms improve their service levels. Although it helps the stable operation of the supply chain, in reality, the degree of altruistic preferences of E-commerce platforms is generally low.
The research conclusions of the article help to complement and improve the theoretical basis of the E-commerce supply chain.

Key words: e-commerce supply chain, altruistic preference concern, product quality, commission