Abstract: With the rapid development of the digital economy, the imitative innovation behavior of platform retailers has become one of the focuses of attention for governments and academia. For example, Amazon's "dual identity" gives it a data and traffic advantage that other merchants do not have. Amazon uses these advantages to monitor and analyze data from third-party merchants on its platform, quickly identifying current best-selling products and products with market potential, and independently developing its own brands or collaborating to develop exclusive brand products. Therefore, for platform retailers with abundant data resources, it is necessary to consider whether to utilize their data advantages for imitative innovation behavior. At the same time, considering the continuous increase in attention to platform monopolistic behavior worldwide, if governments take anti-monopoly regulatory measures, whether platform retailers can still implement these imitative innovation behaviors, and whether these possible anti-monopoly regulations can play a role in protecting innovation, increasing consumer surplus, and social welfare. Based on this, a supply chain model composed of one platform retailer and two manufacturers was constructed, using the classic Hotelling utility function model as the basic function. The model considers three strategic choices for the platform retailer: not engaging in imitative innovation, engaging in independent imitative innovation, and engaging in collaborative imitative innovation. By comparing the profits of the platform retailer, the level of product innovation, consumer surplus, total social welfare, and market concentration under these three strategies, the optimal imitative innovation strategy selection conditions for the platform retailer are provided. The analysis examines the impact of different imitative innovations on product innovation and social welfare, and, in conjunction with existing anti-monopoly rules, designs two regulatory strategies. Additionally, the analysis considers scenarios where imitated manufacturers may switch platforms and where platform retailers provide open data information to manufacturers. It assesses whether these scenarios would change the platform retailer's choice of imitative innovation strategy and whether they can effectively improve the level of product innovation and social welfare. The study aims to provide monitoring, identification, and governance references for government antitrust departments. Research findings: Firstly, government regulations to some extent alter the strategy choices of platform retailers. In the absence of regulations, not engaging in imitative innovation is not the optimal choice for platform retailers; when the government prohibits imitative innovation, independent research, and development become the optimal choice for platform retailers; and when innovation subsidy regulations are implemented, both independent and collaborative imitative innovation may be the optimal choices for platform retailers. Secondly, in the absence of regulations, if the innovation imitation coefficient is small, the highest level of product innovation occurs under independent imitative innovation, while the highest level of product innovation occurs under no imitative innovation if the innovation imitation coefficient is large. Innovation subsidy regulations can enhance the level of product innovation. Thirdly, only when the commission coefficient of switching platforms is relatively small can the level of product innovation be increased, and only then will imitate manufacturers choose to switch platforms. Fourthly, opening data information by platform retailers can enhance the level of product innovation, and the cost of data information will affect the strategy choices of both platform retailers and imitated manufacturers.

Key words: Platform retailers, No imitative innovation, Independent imitative innovation, Collaborative imitative innovation, Antitrust regulation