<bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Background:</b> Zhihu live talks, as a major online knowledge commodity, enable speakers to provide professional information and interact with the audiences. The use of hedges and boosters has been associated with the realization of such a goal. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Literature review:</b> Previous research has indicated the relevance of disciplines or genres in the use of hedges and boosters in academic discourse; however, little is known about the use of these metadiscourse markers in Zhihu live talks as a new register for popularizing professional knowledge. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Research questions:</b> 1. What are the disciplinary variations in the use of hedges and boosters in medical science and health (Med) and education (Edu) live talks? 2. To what extent do speakers’ characteristics (i.e., expertise and community status) have an impact on the use of hedges and boosters in Med and Edu live talks? <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Research methods:</b> We collected the transcripts of 123 Med and 126 Edu live talks, as well as the demographic information of each speaker. Following a framework adapted from Hu and Cao, we conducted an analysis of the frequencies and functions of hedges and boosters, and how they associate with speaker characteristics in each category of live talks. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Results:</b> The two corpora exhibited significant differences in the frequencies and functions of hedges/boosters, and the differences can be attributed to the conventions of knowledge making in medicine and education disciplines. In addition, speaker characteristics have some impact on the use of hedges and boosters, such as speakers’ levels of conformity to disciplinary conventions or their strategic efforts in relational management. <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Conclusion:</b> The findings can guide different speakers to configure metadiscourse to inform, argue, and direct while popularizing professional knowledge of different disciplines.