Objective To explore the association between the preoperative systemic immune-inflammation index (SII) and prognosis in non-small cell lung cancer (NSCLC) patients. Methods A comprehensive literature survey was performed on PubMed, Web of Science, EMbase, The Cochrane Library, Wanfang, and CNKI databases to search the related studies from inception to December 2021. The hazard ratio (HR) and 95% confidence interval (CI) were combined to evaluate the correlation of the preoperative SII with overall survival (OS), disease-free survival (DFS), and recurrence-free survival (RFS) in NSCLC patients. Results A total of 11 studies involving 9 180 patients were eventually included. The combined analysis showed that high SII levels were significantly associated with worse OS (HR=1.61, 95%CI 1.36-1.90, P<0.001), DFS (HR=1.50, 95%CI 1.34-1.68, P<0.001), and RFS (HR=1.17, 95%CI 1.04-1.33, P<0.001). Subgroup analyses also further verified the above results. Conclusion Preoperative SII is a powerful prognostic biomarker for predicting outcome in patients with operable NSCLC and contribute to prognosis evaluation and treatment strategy formulation. However, more well-designed and prospective studies are warranted to verify our findings.