Abstract: Objective To evaluate the value of serum metal matrix protease 8(MMP-8) combined with inflammatory composite indexes for the clinical diagnosis and prognostic evaluation of gastric cancer.Methods A total of 154 gastric cancer patients who were treated in the Affiliated Hospital of Nantong University from March 2016 to April 2017(before surgery and three months after surgery) as well as and 105 healthy subjects from the Health Examination Center were selected and their blood samples were collected. The levels of serum MMP-8 of gastric cancer patients before and after surgery and the levels of serum MMP-8 of the healthy subjects were determined by enzyme-linked immunosorbent assay(ELISA). The relationship between MMP-8 and clinical pathological parameters, leukocyte count and composite indexes of inflammation, including neutrophil to lymphocyte ratio(NLR), pan-immune-inflammation(PIV) and systemic immune inflammation index(SII), were analyzed. The diagnostic efficacy and prognosis evaluation of MMP-8 combined with NLR, PIV and SII for gastric cancer were evaluated by logistic regression and receiver operating characteristic(ROC) curve analysis. Kaplan-Meier method was used to plot survival curves and Cox proportional hazards model was used to analyze univariate and multivariate prognostic factors.Results The levels of serum MMP-8 in gastric cancer patients were significantly higher than those in the postoperative group and in the healthy control group(P<0.05). The concentration of serum MMP-8 in gastric cancer patients was correlated with lymph node metastasis, TNM stage, degree of differentiation, neutrophil count, lymphocyte count, NLR, PIV and SII(all P<0.05). According to ROC curves, serum MMP-8 combined with NLR, PIV and SII significantly improve the diagnostic efficiency and the efficiency of prognosis evaluation of gastric cancer in the early stage. The overall survival of gastric cancer patients in the high MMP-8 group was shorter than that in the low MMP-8 group(P<0.05). Cox multivariate regression model showed that serum MMP-8>117.16 μg/L, SII>545.86 and distant metastasis were independent influencing factors for the overall survival of gastric cancer patients(P<0.05).Conclusions MMP-8 combined with inflammatory composite indexes has high predictive value for the prognosis evaluation of gastric cancer.