Background: Females with ST-segment elevation myocardial infarction (STEMI) have higher in-hospital and short-term mortality rates compared with males in China, suggesting that a sex disparity exists. The age of onset of STEMI is ahead of time and tends to be younger. However, there are relatively little data on the significance of sex on prognosis for long-term outcomes for adult patients with STEMI after percutaneous coronary intervention (PCI) in China. This study sought to analyze the sex differences in 30-day, 1-year, and long-term net adverse clinical events (NACEs) in Chinese adult patients with STEMI after PCI. Methods: This study retrospectively analyzed 1920 consecutive STEMI patients (age <60 years) treated with PCI from January 01, 2006, to December 31,2012. A propensity score analysis between males and females was performed to adjust for differences in baseline characteristics and comorbidities. The primary endpoint was the incidence of 3-year NACE. Survival curves were constructed with Kaplan-Meier estimates and compared by log-rank tests between the two groups. Multivariate analysis was performed using a Cox proportional hazards model for 3-year NACE. Results: Compared with males, females had higher risk profiles associated with old age, longer prehospital delay at the onset of STEMI, hypertension, diabetes mellitus, and chronic kidney disease, and a higher Killip class (≥3), with more multivessel diseases (P < 0.05). The female group had a higher levels of low-density lipoprotein (2.72 [2.27, 3.29] vs.2.53 [2.12, 3.00], P < 0.001), high-density lipoprotein (1.43 [1.23,1.71] vs.1.36 [1.11, 1.63], P = 0.003), total cholesterol (4.98±1.10 vs.4.70±1.15,t =-3.508, P< 0.001),and estimated glomerular filtration rate (103.12±22.22 vs.87.55±18.03, t =-11.834,P< 0.001) than the male group. In the propensity-matched analysis, being female was associated with a higher risk for 3-year NACE and major adverse cardiac or cerebral events compared with males. In the multivariate model, female gender (hazard ratio [HR]: 2.557, 95％ confidence interval [CI]: 1.415-4.620, P = 0.002), hypertension (HR: 2.017, 95％ CI: 1.1 38-3.576,P=0.016),and family history of coronary heart disease (HR: 2.256,95％ CI: 1.115-4.566, P = 0.024) were independent risk factors for NACE. The number of stents (HR: 0.625,95％ CI: 0.437-0.894,P=0.010) was independent protective factors of NACE. Conclusions: Females with STEMI undergoing PCI have a significantly higher risk for 3-year NACE compared with males in this population. Sex differences appear to be a risk factor and present diagnostic challenges for clinicians.