Abstract: Objective: To investigate the feasibility of low-dose CT scanning in the sacroiliac joint of adolescents and to determine its optimal parameters. Methods: With the application of PHILIPS 64-row 128-slice spiral CT scanner, a total of 150 adolescents aged 14~30 years(weight <75 kg and BMI <25) were selected in the study and then randomly divided into three groups. In the conventional dose group, the tube voltage was 120 k V and the tube current was 250 m As; low dose group A applied a tube voltage of 120 k V and tube current of 100 m As, and in low dose group B, the he tube voltage was 100 k V and the tube current was 100 m As. Sacroiliac joints among three groups were scanned. Volume CT dose index(CTDIvol) and dose length product(DLP) were recorded in the CT scanning patterns of the three groups. The image quality was independently scored and averaged by two physicians by using double blind method, scores were averaged. Rank-sum test and variance analysis were used for statistical analysis. Results: The image quality of the three groups could meet the diagnostic requirements, and there was no statistical significance(P>0.05). The radiation dose in low dose group B was significantly lower than that in conventional dose group, showing a significant difference(P<0.05). Conclusion: Low dose scanning technique using tube voltage of 100 k V and tube current of 100 m As can ensure the image quality, meet the diagnostic requirements and significantly reduce the patient's radiation dose.