This study was conducted in a Hong Kong secondary school classroom with a number of 29 students, aiming to investigate how the effects of cooperative learning contribute to students' learning achievement in classroom. Three steps‐Planning, Implementation and Evaluation were adopted in this action research. Quantitative data were collected, including self‐evaluation, peer evaluation and questionnaire, as well as class observation. Statistics analysis was used for evaluating the obtained data. Results positively showed that cooperative learning did motivate students' learning and promote their class achievement. This finding highlighted the importance of cooperative learning and its positive effects on students' learning achievement.