Abstract Objectives The aim of this meta-analysis is to assess the association between obesity and risk of surgical site infections (SSI) risk in orthopedics. Methods We searched the electronic database of PubMed and Web of Science for observational studies about risk factors for SSI risk in orthopedics, meta-analysis of body mass index (BMI) between infection group and no infection group, infection rate in obesity expose and no obesity expose were conducted, respectively. Results A total of 20 studies included in the meta-analysis. The pooled weighted mean difference (WMD) of BMI between infection group and no infection group was 0.329 (95% CI 0.215–0.444), which was statistically significant (z = 5.65, p = 0.000). The pooled relative risk (RR) of infection rate compare obesity expose with no obesity expose was 1.915 (95% CI 1.530–2.396), which was statistically significant (z = 5.68, p = 0.000). No publication bias was found (Begg test P = 0.174 and Egger test P = 0.345) in pooled WMD of BMI. But there was significant publication bias in pooled RR of infection rate (Begg test P = 0.001 and Egger test P = 0.001). Conclusion Our meta-analysis indicates that obesity had about twofold increased risk of surgical site infections risk in orthopedics. However, this conclusion should be verified by further well designed prospective cohort studies.