Abstract: The image quality and the radiation dose are important performance indicator of dedicated breast CT(DBCT). In this paper, the factors of tube voltage and filter were studied by Monte Carlo simulation method which have effect on the image quality and radiation dose which for comprehensive assessing the relationship between them that introduced the dose efficiency η that related to image resolution, noise and radiation dose. Research results show favorable dose efficiency can be gained if reasonable voltage values are selected and that optimization of filter shape can reduce dosage which human body absorbs. Therefore, rational setting of parameters can decrease radiation dose and provide significant reference for clinical application of dedicated breast CT while guaranteeing image quality as far as possible.