Lesson Study (LS) as a collaborative learning approach for teacher professional development remains an area of critical interest for educational professionals. Most studies focus on the benefits and defects of LS practices implemented in the subject of mathematics or science, and in primary and secondary schools rather than English language teachers at the tertiary level. The research reported here focused on how LS might influence College English teacher’s professional development within the context of College English educational reform in China.

Based on an adaptation of Dudley’s (2014) LS model, this research adopted a qualitative research method of Grounded Theory (Glaser & Strauss, 1967) in the teachers’ four- week LS practice to collect and analyze data. Data source included observation of teachers’ teaching and meetings, and semi-structured interviews from 11 teachers in two groups of College English courses and two administrators, as well as documents related to this LS practice. Data were open-coded through a thematic analysis assisted with NVivo software to investigate the characteristics of the LS approach through comparing it with Collective Lesson Preparation (CLP), what teachers learned and developed in the LS learning community, and what impact the LS practice had on teacher professional development.

Findings showed that compared with CLP, the LS approach generated lesson plans which were more easily implemented, had more specific and in-depth practice of all the teaching steps, was implemented continuingly on a regular basis with a long-term goal, valued the process of group planning, observation and reflection, and put students as the focus. The teachers enriched their teaching knowledge and improved their teaching repertoire (mainly about prioritization of teaching focus and about teaching design or conception) through the intervention of the LS practice. The teachers experienced six positive impacts of LS in peer modelling, expanding teaching ideas and skills, self-reflection, collaboration in common planning time, awareness of LS, and research enthusiasm. However, several teachers were distracted by the excessive amount of ideas, felt restricted by less flexibility of unified lesson plans, and were concerned with the constructive feedback element.

Based on findings, this research first discussed implications for how the LS practice was applied. It extracted four focal factors (teacher, organizer, expert, and time) that might improve the effectiveness and sustainability of the LS implementation, as well as systematic policy support. As for the theoretical implication, an Experiential LS Learning Cycle was proposed, contributing to the literature on LS within an Asian context and to the development of Experiential Learning Cycle as well. This research also pointed out prospects of LS like online LS.