Objective To assess the clinical value of unenhanced 64-slice spiral CT combining ureteral curved planar reformation(CPR) technique on diagnosis of latent ureteral calculi. Methods 68 patients with ureteral calculi underwent unenhanced 64- slice spiral CT scan. Reconstructed images (slice thickness=0.625mm) were transferred to CT workstation to reformat the whole ureters images by CPR. To observe the location and size of ureteral calculi by comparing axial images and the whole ureters images reformatted by CPR. Results 53 out of all 68 patients were diagnosed ureteral calculi by axial images. Due to small size of calculi, anatomical location affected by vascular calcification and phlebolith, definite diagnosis could not be made by axial images for the other 15 cases. The whole ureters images reformatted by CPR of all 68 patients showed positive results and displayed the size and location of all 97 calculi (0.3-0.8cm), which 32 calculi were located in upper ureters, 21 calculi in middle ureters, 44 calculi in lower ureters. 30 cases of 37 calculi were in right ureters, while 28 cases of 33 calculi were in left ureters and 10 cases of 27 calculi in both ureters. Conclusion Unenhanced 64-slice spiral CT combining ureter curved planar reformation can achieve whole ureters images with good imaging quality and display ureteral calculi accurately, it has great important value in clinical diagnosis and differential diagnosis of ureteral calculi.