This article explores the paradox between the closing gender gap in math performance and the persistent gender gap in STEM aspiration using data from the Chinese Education Panel Survey (CEPS). Extending the stereotype threat literature, this article includes measures of gender-math stereotypes from students, parents, and peers, and offers an analysis to address the limitations of previous studies. Findings indicate that gender-math stereotypes are associated with a gender gap in students' self-assessment in math-learning competency, even after controlling for math performance; this self-assessment is further associated with students' aspiration in science and engineering careers. Moreover, the effect of math self-assessment on science and engineering aspiration is stronger among girls than boys. However, even after controlling for math self-assessment and gender-math stereotype, boys are still more likely to aspire to careers in science and engineering than girls. This article discusses policy implications of the findings.