Abstract: The rapid development of content technology on new media platforms has constructed a new picture of knowledge dissemination which promts the rise of subculture in the knowledge area and gives rise to a large number of culture communities highly-focused by youth subculture groups. Based on the MOA(Motivation-Opportunity-Ability) model and the communication effect research paradigm, combined with the research into youth subculture video platform and cultural communities called Bilibili, the study focuses on conducting empirical analysis on a typical video-based knowledge dissemination case whose name is "Luoxiang interprets the Criminal Law", and finds that motivation is the main driving force of knowledge dissemination, opportunity creates an open-flowing space for knowledge dissemination and ability contributes to the positive cycle of knowledge dissemination effect, which jointly construct the development space of knowledge dissemination on Bilibili, making knowledge video plays a unique role in pan-entertainment and highly-gathered youth culture and building a strong fusion link between knowledge dissemination and youth subculture.