Abstract: Objective To Study the value of in ¹⁸F-FDG SPECT/CT (¹⁸F-FDG coincidence single photon-emission computed tomography/multi-detector computed tomography) in the evaluation of treatment response in gastric cancer. Methods MDCT (multi-detector computed tomography) enhancement scanning and ¹⁸F-FDG SPECT/CT was performed in 31 untreated patients with diagnosed gastric cancer. Then, chemotherapy with FOLFOX4 4Cycles was administrated on the 31 patients. 2 weeks after four Cycles of chemotherapy, both MDCT and ¹⁸F-FDG SPECT were performed in 31 patients. Criterion in MDCT was used to evaluate the treatment response. Then, the value of T/B was discussed by the treatment response. Results Kappa coefficient of the values of R_△T/B 1-(T/B)_{after chemotherapy}/(T/B)_{before chemotherapy} of ¹⁸F-FDG SPECT/CT and R_△MD (1- MaxiDiameter_{after chemotherapy}/MaxiDiameter _{before chemotherapy}) of MDCT is 0.867（P<0.01）.The accuracy of R_△T/B to predict the treatment response is 94.3%. If we make the base line of R_△T/B as 35%, The sensitivity, specificity, positive predictive value，negative predictive value of ¹⁸F-FDG SPECT/CT were 100%, 94.1%，93.3% and 100% respectively. If R_△T/B is 40%,the results are 85.7%,100%,100% and 89.5% respectively. Conclusion The changed rate of the value of T/B in ¹⁸F-FDG SPECT/CT in gastric cancer is accurate and feasible. We recommend the value of T/B decrease more than 35% as the demarcation of Objective remission and No remission.