Video course previews provide customers with direct product experience, which can reduce information asymmetry relating to knowledge products and promote purchases. Some research has proved the effects of previews. However, little research focuses on the interaction effects between video course previews and extrinsic cues of products, and there is even less research on intrinsic cues provided by video course previews. To address these issues, we study the interaction effects between extrinsic cues and video course previews on purchase decisions. Additionally, we further explore the effects of intrinsic cues provided by video course previews based on cue utilization theory. We empirically test the model using data from a large medical knowledge payment platform. To our knowledge, this is the first study that attempts to provide a better understanding of the effects of intrinsic cues. We find some interesting results. For example, more interrogative sentences in the video course previews can prompt purchase. In contrast, using excessive first-person pronouns in the video course previews negatively affects consumers’ purchase behaviors. These new findings have direct implications for platforms to optimize the previews; more broadly, the findings can facilitate better understanding of the influence mechanism of video course previews on knowledge payment platforms.