Abstract: Objective: To explore the influence of GSI data in different pitch of single source-dual energy CT. Method: AGE standard water model was imaged by different scanning pitch of single source-dual energy CT (Discovery CT 750 HD). Scanning parameter: 6 Scan Protocols with tube current form 180 to 192.5 mAs, medium FOV, thickness 5 mm, and two different pitch (1.375: 1 and 0.984: 1) for scanning. 6 slices of images was acquired in succession for each 12 groups of data and reconstructed 1.25 millimeter-thickness images. Using GSI general MD analysis software for image processing, 5 ROIs (3000 mm²) were putted in the middle and 3, 6, 9, 12 o'clock direction. CT value and CT SD value were measured on the 70 keV monochromatic image, water-iodine value and water-iodine SD value were measured on the water-iodine concentration image. Independent-samples t test were used for statistical analysis. Result: The CT value of 1.375: 1 group and 0.984: 1 group were (1.390±1.90) HU and (1.969±1.74) HU, SD value were (7.21±0.55) HU, (6.47±0.56) HU; 1.375:1 group were closer to the standard value. The water-iodine value of 1.375mm group were 1001.56±1.76, SD value were 4.95 ±0.43; the water-iodine value of 1.375: 1 group and 0.984: 1 group were 1001.95 ±1.47, 1002.19±1.34. Differences between the two groups have statistical significance (P〈0.05). Conclusion: Scanning pitch influenced GSI data. Using smaller pitch scanning condition, the reliability of diagnosis can be improved.