This study aimed to explore the direct impact of parental autonomy support and school belonging on the meaning of life from the positive psychology perspective and to verify whether self-efficacy can contribute to the meaning of life based on social cognitive theory. The participants were 7529 Hong Kong secondary school students in grades 10 to 12 from the PISA 2018 survey. This study applied structural equation modeling to verify the mediating effect of self-efficacy on the relationship between parental autonomy support, school belonging, and meaning in life. In addition, This study found no significant differences between boys and girls in a multi-group model comparison. The results indicate that both boys and girls need parental autonomy support and school belonging to enhance their self-efficacy and thus enhance their meaning in life. This study also provided a new perspective and research theoretical model for positive psychology to improve secondary school students' meaning in life.