Objective To explore the application of low-dose CT scanning combined with iterative model reconstruction (IMR) technique in preoperative diagnosis of breast cancer. Methods A total of 60 cases of breast cancer in our hospital from December 2014 to November 2017 were selected and given CT scanning of breast and chest. Image reconstruction was carried out by using iterative model reconstruction (IMR) and filtered back-projection reconstruction (FBP) respectively. The objective image quality [CT value, noise (SD) value and contrast noise ratio (CNR) of regions of interest] and subjective image quality [lesion contour, artifact, noise and image definition] were compared between the two technologies. Results There was no significant difference in the CT value of breast regions of interest between the IMR technique and the FBP technique (P>0.05), and the SD value was significantly lower than that of the FBP technique (P<0.05) while the CNR was significantly higher than that of the FBP technique (P<0.05). The scores of lesion contour, artifact, noise and image definition of breast by the IMR technique were significantly higher than those by the FBP technique (P<0.05). The scores of artifact, noise and image definition of chest by the IMR technique were significantly higher than those by the FBP technique (P<0.05). The total dose of CT scanning was (5.21±1.06) mGy, and the total ED was (2.20±0.41) mSy. The total dose of breast dynamic scan was (1.68±0.49) mGy, and the ED was (0.63±0.19) mSy. Conclusion Low-dose CT scanning combined with IMR technique has good image quality and has important clinical value in preoperative assessment of breast cancer.