Social e-commerce has become a widely studied paradigm in the Web 2.0 era. We explore the impact of opinion leaders' interaction quality (IQ) on platform brand value from the perspective of prosumption and examines the mediating effect of customer engagement and the moderating effect of prosumers capability (PC). Data were collected from 318 e-commerce users from social e-commerce platforms via questionnaire. Structural equation modeling was used to examine the model and bootstrap sampling technique via AMOS 23.0 and Process macro model 17 was applied to test the proposed hypotheses. Findings indicate that IQ brings a more positive impact on customer engagement, and customer engagement also affects the platform's brand value. Meanwhile, customer engagement plays a significant mediating effect while the PC has different moderating effects in different pathways. This paper, examines the principle of IQ on platform brand value based on the logic of prosumption. Results indicated that social e-commerce platform should keep a close watch on the effect of opinion leaders on the platform, improve customer engagement by improving the inner emotional experience of platform users, and thus enhance the platform brand value.