PURPOSE To evaluate the feasiblity of low-dose CT combined with adaptive statistical iterative reconstruction(ASIR)in the diagnosis of urinary calculi METHOD AND MATERIALS 70 patients with clinically suspected urolithiasis were included.Followed by both conventional-dose CT scans(CDCT) and low-dose CT scans(LDCT).Automatic tube current modulation scanning was used,with a noise index setting of 13 in CDCT and 25 in LDCT.Image were reconstructed with filtered back projection(FBP)and different settings of ASIR(40%、60%、80%).Calculi(size、location、number)、image quality(scale,1-5)、image noise(scale,1-3)and confidence levels for urolithiasis diagnose(scale,1-3)were evaluated and measured by two radiologists independently.Radiation dose by dose length product(DLP) were recorded,and effective dose(ED)was calculated.Statistical analysis was performed with Mann-Whitney U test and paired t tests RESULTS Mean ED was 2.07 mSv in LDCT compared with 6.12 mSv in CDCT(P<0.05),.which decreased by 66.1%.LDCT-80%ASIR images showed great image quality(score,4.09),which was similar to CDCT-FBP images(score,4.17)(P>0.05),but higher than LDCT-FBP images(score,2.77)(P<0.05) CONCLUSION Combined with automatic tube current modulation scanning and ASIR,radiation dose can be significantly reduced with image quality maintained.