Purpose: To investigate the prognostic value of pretreatment albumin to alkaline phosphatase ratio (AAPR) in human cancers.Methods: Several electronic databases were searched up to Jan 4, 2020 for relevant studies. The prognostic value of AAPR were assessed by pooled hazard ratios (HRs) with their corresponding 95% confidence intervals (CIs). The endpoint events included the overall survival (OS), disease-free survival (DFS), cancer-specific survival (CSS) and progression-free survival (PFS).Results: A total of 15 articles involving 20 studies with 6062 cancer patients were included. Our results proved that low pretreatment AAPR was related with poor OS (HR=1.83, 95% CI: 1.66-2.02; P<0.001), DFS (HR=1.97, 95% CI: 1.49-2.61; P<0.001), CSS (HR=1.88, 95% CI: 1.37-2.56; P<0.001) and PFS (HR=1.74, 95% CI: 1.24-2.43; P=0.001). In addition, the significant correlation between pretreatment AAPR and OS was not affected by the treatment strategy and tumor pathological type.Conclusion: Low pretreatment AAPR is related to poor prognosis in human cancers, and AAPR could be served as a promising prognostic indicator in cancer patients.