Abstract: As a new organizational form rising rapidly under the development of digital economy, platform has become the core subject of the development of new forms of platform economy by connecting and integrating upstream supply resources and meeting the needs of downstream small retail enterprises. This paper constructs a supply chain network consisting of multiple brand operators, distributors (platform operators and traditional distributors), micro-sized retailers and demand markets, describes the optimal operation strategy and equilibrium conditions of supply chain members by using variational inequality, and reveals the influence of micro-sized retailers’ fair concern behavior and platform service level on equilibrium decision-making at all levels of the supply chain. The results show that when considering the fair concern behavior of micro-sized retailers under the platform operation mode, the greater the concern degree is, the higher the profit of the main body of the supply chain network will be, thus providing the possibility for small retailers to realize fairness. When the service level of the platform improves, the corresponding service cost increases. When the service level is within the range of [0.3,0.5], it is conducive to the overall coordination of the supply chain. The overall profitability of the supply chain is better when both the equity concerns of small retailers and the level of service provided by the platform are taken into account than when only one of the factors is taken into account.

Key words: platform economy, supply chain network, fairness concerns, network equilibrium, variational inequality