Consider that online platforms have access to private consumer quality preference information about the relationship between quality and demand, and help brands to pinpoint product quality through strategic sharing. This paper studies the information sharing of product quality positioning of e-platforms towards competing brand owners. The results show that regardless of the actual quality preferences of the consumers, the platform can mitigate competition between the two brand owners by adopting an asymmetric information sharing strategy, as long as the level of competition in the market is high. This is because the information gap can help the brand owners to differentiate and position their products, thus mitigating competition. In addition, low-priced products resulting from precise targeting by brands can lead to low returns when actual consumer quality preferences are lower than average quality preferences. Therefore, the platform should not share information to both parties in most cases. Interestingly, if actual consumer quality preferences are much lower than average quality preferences and the level of competition is sufficiently low, the gains from sales volume are sufficient to compensate for the low pricing losses, and the platform should adopt a symmetric information sharing strategy. On the contrary, when consumers' actual quality preference is higher than the average quality preference, high-priced products resulting from brands' precise positioning will yield high returns to some extent, as long as the market is not highly competitive. Therefore, the platform should adopt a symmetric information sharing strategy in most cases. Our findings provide useful guidance on how online platforms can share information with competing brand owners in the face of varying levels of consumer preference. In addition, under the scenario of asymmetric market share between two brands, the wider the gap between their market shares, the more the platform should take advantage of the information gap to help differentiate the brand's products and thus achieve sustainable profit growth.