Informed by literature on developing pedagogical content knowledge (PCK) through teacher collaboration, this study aims to investigate the trajectory of PCK development among business English teachers through module team collaboration in Chinese context. Drawing upon multiple sources of data including observation, semi-structured interview, and teaching materials from three case teachers, this study explores how PCK components were developed in one academic year when case teachers participated in module team collaborative activities. The findings show the individual differences among the three participants in their PCK development and reveal that two key PCK components--Knowledge of students' understanding and Knowledge of instructional strategies have developed through teacher collaboration. This study suggests the collective inquiry in teacher collaboration.