Abstract: Objective: Evaluate CT enhanced urinary tract imaging (CTU) using automatic tube current modulation (ATCM) technology and the fixed tube current technology influence on image quality and radiation dose, further deepen understanding of ATCM technology. Methods: 100 patients with clinical history of urinary tract obstruction were randomly divided into fixed tube current and ATCM group (<i<n</i< = 50) were separately stage renal cortex, essence and excretion scanning, fixed tube current group: 400 ma. ATCM groups: tube current 150 mA and 500 mA, noise figure 12 HU (IN), the rest of the two groups the same scan parameters, the original data to AW workstation 4.2 respectively through multiple planar reconstruction (MPR), curved surface reconstruction (CPR), volume reprcsentation (VR) and maximum density projection (MIP). Record volume CT dose index (CTDIvol), dose length product (DLP), and calculate the effective dose (ED); By two deputy director of the physician to subjective and objective image quality evaluation, evaluation content includes: image signal-to-noise ratio (SNR), contrast to noise ratio (CNR) and ureteral display the location, scope, nature and obstruction. By using two independent samples t test to compare the clinical data of two groups, radiation dose, the diagnosis and surgical results in positioning, qualitative accuracy of ureteral obstruction. Results: In the two groups in gender, age, body mass index (BMI) were no statistical difference (<i<P</i<<0.05). ATCM group of patients receiving radiation dose group was significantly lower than the fixed tube current, the differences between the two groups have significant statistical significance (<i<P</i<<0.05). Two groups of the subjective and objective evaluation of image is not statistically significant (<i<P</i<<0.05), surgery, scope, nature and in the diagnosis of diagnostic results have good. Conclusion: ATCM technology application in CTU is feasible, and obviously reduce the radiation dose of patients, is worth to be widely applied in clinical.