China's education reforms might affect students' academic emotions (and hence their motivation and learning outcomes). This study examines Chinese adolescents' academic emotions across time via a cross-temporal meta-analysis of 96 studies published between 2004 and 2017. Our results indicate that in later years, adolescents' positive high-arousal and positive low-arousal emotions were higher, while negative low-arousal emotions were lower. Compared to 2004, positive high-arousal and positive low-arousal emotions in 2017 were both over half a standard deviation higher, while negative low-arousal emotions were over half a standard deviation lower. Positive high-arousal and positive low-arousal emotions were higher in later years in Eastern China but not in Central China and Western China. In later years, negative low-arousal emotions were lower in Eastern and Western China than in Central China. Gender differences were not significant. These results are consistent with both control-value theory and the claim that curriculum and instruction reform helped improve students' academic emotions in China.