The flipped classroom is one the most popular teaching models in recent years. Domestic and international scholars have carried out many experimental and quasi-experimental studies to explore the impact of flipped classroom on students' academic performance, but the results are mixed. To further explore the impact of flipped classroom on college students' academic performance, this paper adopted the meta-analysis method to quantitatively analyze 20 domestic and international experimental studies of flipped classroom. We found that: (i) The flipped classroom positively affected college students' academic performance, and the overall combined effect size was 0.66; (ii) Effect sizes vary somewhat by subject types. For example, effect sizes for science, liberal arts, and engineering were 0.75, 0.72, and 0.34, respectively; (iii) The flipped classroom had the same effect on the learning effect of different knowledge types, but practical knowledge learning was better than theoretical knowledge; and (iv) The flipped classroom had produced significant impact on different class sizes, particularly medium class size.