Web discussions are an effective tool for academic help-seeking. However, the current design of online forums does not guarantee the quality of academic help-seeking. One of the course-centred forums can lead to confusion as help seekers and helpers are asynchronous. Therefore, this study conducted a quasi-experimental study in which students were divided into an experimental group (N=S2) and a control group (N=48) by designing a sub-topic discussion scaffold capable of prompting in the learning platform. The system sends help-seeking prompts to students in the experimental group, inviting them to access a dedicated sub-discussion area under each topic to ask or answer questions, while students in the control group do not receive prompts. Through analysis of students' social networks and learning behaviour, the scaffolding design of sub-discussion areas and prompting students to enter them can promote students' participation in online learning help-seeking and enhance the effectiveness of online learning.