The expression of P53 was previously found by us significantly correlated with maximal standardized uptake value (SUVmax) in non-small cell lung cancer (NSCLC) patients. Hence, the aim of this study was to clarify the relationship between SUVmax and the status of the chemotherapy-related tumor marker expression or serum tumor markers in gastric adenocarcinoma patients. Sixty-four gastric adenocarcinoma patients who underwent 18F-FDG PET/CT prior to treatment were enrolled in this study. Immunohistochemistry was performed to detect changes of Her-2, P53 and Survivin in lesions, and electrochemiluminescence (ECL) method was used to quantify expression of serum CA72-4, CA19-9 and CEA of these patients. Then, the relationships between these parameters above were assessed by Spearman correlation analysis. Also, receiver-operating characteristic (ROC) curve was performed to determine the best cut-off value of SUVmax for suggesting chemotherapy resistant tumor markers. Besides, we identified a linear correlation to estimate the equations between SUVmax and the serum tumor markers. Our results showed that higher SUVmax was detected in patients with positive expression of Her-2 and P53, compared with negative groups. The Spearman correlation analysis showed that SUVmax was associated with Her-2 or P53 with the moderate relevant Pearson correlation coefficient. ROC curve analysis showed that the sensitivity and specificity of SUVmax for suggesting Her-2 or P53-positive, when the cut-off value of SUVmax was set at 3.25 or 5.45, respectively. Moreover, the relationship between SUVmax and serum tumor markers were analyzed by linear correlation analysis, and serum CA72-4 and CA19-9 could be used as independent parameters to establish an equation for SUVmax by the linear regression models. These results suggested that SUVmax of 18F-FDG PET/CT could be used to predict and evaluate Her-2 or P53 related chemotherapy resistance of gastric adenocarcinoma patients. However, before PET/CT scanning, serum tumor markers could be used to calculate the SUVmax approximately.