This paper reports the effect of Learning Study module on developing the teaching competency of pre-service teachers in Hong Kong. Learning Study module is a research based teacher training course that aims to improve pre-service teachers’ lesson preparation skills and their teaching competency. The module is offered for all Year Two students in the Bachelor of Education programme of the Hong Kong Institute of Education. It comprises a series of lectures, consultation meetings and teaching practices that set the theoretical framework for conducting Learning Study. Activities are organized in such a way that pre-service teachers can practice argumentation, decision making and justification while investigating and solving pedagogical problems. This study aims to validate a theoretical model for exploring the critical successful factors of the Learning Study module for nurturing pre-service teacher’s reflective competency and lesson preparation skills through a quasi-experiment design. 341 preservice teachers took part in a questionnaire survey. A structural equation model was applied to explore the relationships. Lesson analysis, framework for conducting Learning Study, consultation on lesson design and teaching, lesson implementation and peer observation in the teaching practices are identified to be the critical successful factors for developing lesson preparation skills, teaching competency and reflective experiences of the pre-service teachers.