Objective To investigate the value of spectral CT with iodine parameters in distinguishing moderately-differentiated adnocarcinoma from poorly-differentiated adenocarcinoma.Methods 61 patients with gastric adenocarcinoma underwent preoperative CT scanning that included arterial phase(AP) and venous phase(VP) with gemstone spectral imaging(GSI) mode.All measurements were performed on the GSI viewer.The iodine concentration (IC) and the water concentration (WC) of the primary lesion were measured.Then the normalized iodine concentration (NIC) and contrast enhancement ratio (CER) were calculated.The CT values were measured at 70 keV Mono image.All the values of CER, NIC, IC and WC in the primary lesion were recorded and assessed by independent-samples t test.Receiver operating characteristic (ROC) was used to determine the threshold of IC and NIC for differentiating poorly-differentiated adenocarcinoma and moderately-differentiated adnocarcinoma.Results The IC values between moderate differentiation group and poor differentiation group were 8.73±4.05 vs 11.07±4.80(100 μg/cm3) in AP and 16.89±4.89 vs 21.18±5.96(100 μg/cm3) in VP.The values of NIC between moderately differentiated group and poorly differentiated group were 0.10±0.06 vs 0.13±0.06 in AP and 0.38±0.10 vs 0.49±0.12 in VP respectively.Significant difference of NIC (tVP=3.38, PVP<0.01) and IC (tVP=2.87, PVP=0.01) were only found between poor differentiation group and moderate differentiation group in venous phase.The value of WC and CER (both P>0.05) in double phases revealed no significant difference between the two groups.Conclusion Iodine quantitative parameters of spectral CT can be potentially used to preoperatively evaluate the differentiation degree of gastric adenocarcinoma.Thus, the iodine parameters can reflect the differentiation degree of gastric adenocarcinoma.