Abstract: Objective To explore the clinical value of the upper airway low-dose spiral CT applied in the obstructive sleep apnea and hypopnea syndrome(obstructive sleep apnea hypopnea syndrome,OSAHS). Methods One hundred and twenty patients OSAHS were divided equally into the experimental group and the control group.All patients were underwent the upper airway low-dose spiral CT scanning during the four different states of breathing,calm,the end of deep inspiration and deep expiration,inspiration closed mouth and nose.The tube current of the experimental group used low-dose was 50 mA,the control group used the regular dose was 360 mA.The values of the volumetric CT dose index(CTDI_vol),dose length product(DLP) and the effective dose (effective dosed,E) for each case were respectively recorded.The CT value of ROI in each case was measured on the same tongue position,and the Standard Deviation(SD) of CT value and the Standard Deviation (SD) of CT value was also recorded.The double-blind method was used to subjectively evaluate the image quality,and overall image quality was assessed using a 3 grading scale(excellent,good,poor),then,statistical analysis was done with related data. Results There was no significant difference in length of scanning between the experimental group and the control group,compared to control group,significant differencens in DLP and E value were observed(t=108.252,P<0.001) and CTDI_vol,DLP,E value in experimental group decreased by 87.5%.Signal-Noise Ratio decreased significantly in experimental group(SNR value 6.31±1.75 vs. 10.17±3.13 respectively,t=3.19,P=0.006).Compared to control group,noise increased significantly in experimental group(SD value 25.74±2.61 vs. 1.70±0.17 respectively,t=29.022,P<0.001).Subjective evaluation of image quality with control group was mainly excellent,and mainly good with experimental group,only three cases were of poor-grade,but it did not influence the measurements and diagnostics. Conclusion Scanning of upper airway in OSAHS with 50 mA low-dose can reduce radiation dose significantly,dose not affect the measurement and diagnosis of airway,and has practical value clinically.