Published studies on SPOC provided inconsistent findings regarding its effectiveness. Adopting a meta-analysis method, this study combined the results of 32 experimental and quasi-experimental studies published in the past 8 years in China for analyzing the overall effect size of SPOC for improving student learning in vocational schools. Data analysis confirmed that SPOC has a moderate positive effect, with a combined effect size of 0.592 (P<0.05). Further analysis revealed three significant factors that moderate the effect of SPOC, including discipline area, group size, and knowledge type. SPOC has a larger effect size for disciplines of engineering technology and medical education than of natural science, and humanities and social science. Integrating SPOC for a small to medium-sized group with no more than 50 students brings about significant improvement in learning outcomes. Compared to declarative knowledge, SPOC is effective for developing procedural knowledge. The findings support the adoption of SPOC in vocational education. To amplify its impacts, multiple factors need to be carefully considered in the design and implementation.