There is still a lack of relevant studies on surgical site infection (SSI) after emergency abdominal surgery (EAS) in China. This study aims to understand the incidence of SSI after EAS in China and discuss its risk factors. All adult patients who underwent EAS in 47 hospitals in China from May 1 to 31, 2018, and from May 1 to June 7, 2019, were enrolled in this study. The basic information, perioperative data, and microbial culture results of infected incision were prospectively collected. The primary outcome measure was the incidence of SSI after EAS, and the secondary outcome variables were postoperative length of stay, ICU admission rate, ICU length of stay, 30-day postoperative mortality, and hospitalization cost. Univariate and multivariate logistic regression were used to analyze the risk factors. The results were expressed as the odds ratio and 95% confidence interval. A total of 953 patients [age 48.8 (SD: 17.9), male 51.9%] with EAS were included in this study: 71 patients (7.5%) developed SSI after surgery. The main pathogen of SSI was Escherichia coli (culture positive rate 29.6%). Patients with SSI had significantly longer overall hospital (p < 0.001) and ICU stays (p < 0.001), significantly higher ICU admissions (p < 0.001), and medical costs (p < 0.001) than patients without SSI. Multivariate logistic regression analysis showed that male (P = 0.010), high blood glucose level (P < 0.001), colorectal surgery (P < 0.001), intestinal obstruction (P = 0.045) and surgical duration (P = 0.007) were risk factors for SSI, whereas laparoscopic surgery (P < 0.001) was a protective factor. This study found a high incidence of SSI after EAS in China. The occurrence of SSI prolongs the patient's hospital stay and increases the medical burden. The study also revealed predictors of SSI after EAS and provides a basis for the development of norms for the prevention of surgical site infection after emergency abdominal surgery.