Objective:To investigate the feasibility of reducing the radiation dose on coronary artery calcium score (CS) of virtual non-contrast (VNC) scanning in dual-layer spectral coronary CT angiography(CCTA).Methods:One hundred and twenty-two patients were examined on a dual-layer spectral detector CT scanner from March 2019 to August 2020. Volume CT dose index (CTDI vol), dose length product (DLP), effective dose ( E) were all evaluated for each patient. CS was calculated from both true non-contrast (TNC) and VNC images for left anterior descending (LAD), left circumflex (LCx), right coronary artery (RCA), and the total coronary artery (Total) by two radiologists independently. Pearson′s correlation coefficient was calculated for measuring the association between variables. The correction coefficients of each branch (λ LAD, λ LCx, and λ RCA) and the average correction coefficient (λ AVG) of the total coronary artery were obtained. The calibrated calcium score (CCS_VNC) was equal to λ multiplied by CS_VNC. The CS_TNC and CCS_VNC were compared using repeated oneway analysis of variance test. Correlation analyses for CS_TNC and CCS_VNC and agreement evaluation with Bland-Altman-Plots were performed. Results:The average effective doses in TNC, CCTA and total group were 0.69, 6.47 and 7.16 mSv, respectively. The effective dose was reduced by 10.6% and the scan time was reduced by 39% while using VNC images. There were significant differences among the CS_TNC and CS_VNC of LAD, LCx, RCA and Total ( t=6.75, 5.33, 4.99, 6.60, P< 0.05). Excellent correlations were observed between CS_VNC and CS_TNC ( R2 values were 0.929, 0.896, 0.958, and 0.918; λ values were 2.18, 1.18, 2.15, and 2.07, respectively). There were no significant statistically difference among the CS_TNC, CCS_VNC AVG, and CCS_VNC LAD/RCA of the LAD and RCA (all P> 0.05). The difference was statistically significant among the CS_TNC, CCS_VNC AVG, and CCS_VNC LCx of the LCx ( F=10.94, P<0.05). The paired comparison were performed in groups and the differences were statistically significant between the CS_TNC versus CCS_VNC AVGand CCS_VNC AVG versus CCS_VNC LCx ( t=3.31, 3.43, all P<0.05). There was no significant statistically difference between the CCS_VNC LCx and CCS_VNC AVG( P>0.05). Conclusions:It was feasible to accurately evaluate the CS_VNC from spectral data in comparison to TNC imaging, and to reduce the patient radiation dose and acquisition time.