Objective:To investigate the feasibility of optimization of coronary computed tomography angiography (CCTA) with pre-scan size-specific dose estimate(SSDE).Methods:Ninety patients from Quzhou People′s Hospital during March and May 2018 who underwent CCTA were defined as modelled patients, the regression equation of body mass index (BMI) and water-equivalent diameter ( dw) were conducted and upper quartile of CTDI vol values was calculated. Other 67 patients were divided into two groups: control group (CCTA scan protocol, based on CTDI vol) and study group (CCTA scan protocol using SSDE). The image quality and radiation dose including breast dose (Dose bre) in two groups were assessed. Results:The positive correlation was found between BMI and dw with a linear regression equation of dw=9.241 + 0.644×BMI( r=0.823, P<0.05), and the upper quartile of CTDI vol was 7.92 mGy. The proportions of high-level image quality were 94.10% (367/390) and 93.93% (402/428) in the control and study groups, respectively ( P>0.05). The median signal to noise ratio (SNR) and contrast to noise ratio (CNR) were 21.08/24.39, 17.24/19.94 in the control and study groups, respectively ( P>0.05). The CTDI vol, SSDE and Dbreof the study group were reduced by 37.04%, 35.77% and 37.37% compared with the control group, and statistically significant differences were found( z=-7.041, t=18.479, 15.079, P<0.05) among them. Conclusions:The CCTA scan protocol based on the pre-scan SSDE can significantly reduce the radiation dose and provide the diagnostic image quality.