OBJECTIVE The present study was designed to investigate whether AJCC/UICC 8th edition staging system precisely differentiated patients with different prognosis of gastric cancer (GC). METHODS There were 540 GC cases included in this study. Stratification was done according to the 7th and 8th AJCC/UICC tumor-node-metastasis (TNM) staging systems. Detailed comparison was conducted between two editions in terms of the sub-classification of pN3 stage, redefinitions of stage III, homogeneity, discrimination power, predictive accuracy, and complexity. RESULTS Compared to the 7th edition, the 8th TNM staging system performed better by incorporating pN3a and pN3b into the final stage of GC (P<0.001), had better stage grouping homogeneity (P<0.001), prognostic value (area under the curve, AUC-value was 0.809), and comparable discrimination power. CONCLUSIONS AJCC 8th TNM staging system showed improved efficiency in GC prognosis.