Role-play conforms to the age characteristics of primary school students, which effectively improves the students’ interests and their scores. However, study of application of role-play in the course “morality and rule of law” still remains unclear. Herein, the major aim of the present study is to investigate the effect of role-play on morality and rule of law course in primary school. A total of 41 students were chosen for this study from a primary school in Liwan district, Guangzhou. A designed course of role-play was conducted based on the initial status of students and the standard of morality and rule of law. Three tests, including pretest, immediate posttest and delayed posttest, were carried out to reveal the influence of role play on morality and rule of law course, which were accompanied with an interview for 20 students. Results showed that the scores of immediate posttest and delayed posttest were significantly higher than those of pretest. Moreover, students preferred role play in the class, which could help them to deeper understand the morality and rule of law, suggesting that role-play effectively promoted the performance of morality and rule of law for the students, as well as improved their enthusiasm and motivation in this course. Collectively, this study provided basis information of the application of role-play in morality and rule of law, which inspired the promotion of role-play for other courses.