The concept of 'professional capital', which consists of human, social, and decisional capital, has been adopted in many countries to guide teacher development and school practice. However, more empirical research needs to be conducted to understand the concept in the Chinese context. The study investigates how teachers accumulate their professional capital in Master Teacher Studios (MTSs), a cross-school teacher professional learning community in China. The study adopts a qualitative case study approach. Interviews, observation, and document analysis were employed to collect data from 10 MTSs in Zhejiang province, China. Ten MTS hosts and 28 studio members were selected as research participants. A combination of inductive and deductive coding approaches helped identify specific practices related to the three components of professional capital. Teachers in MTSs develop their human capital with increased professional competence, professional achievements and reputations, as well as enhanced confidence and open mindsets. Regarding social capital, teachers benefit from harmonious interpersonal relationships within MTSs to win peer support, from stronger social ties to learn from experts, and access more visible opportunities to display themselves professionally. They also enhance their decisional capital in the critical areas of teaching research ("jiaoyan") and leadership issues. The study reveals specific practices associated with professional capital in the Chinese context where interpersonal relationships ("guanxi") and cooperation are particularly emphasised, contributing to theory development. The study also describes how teacher leaders contribute to developing teacher professional capital, which may contribute to understanding teacher-led professional learning.