Objective To investigate the detection condition of ultrasound, x-ray mammography and CT on diagnosis of breast cancer. Methods 208 cases with breast cancer in our hospital from July 2015 to July 2017 were selected and divided into four groups according to throwing method. 52 cases given ultrasound, x-ray mammography and CT were respectively seen as control groupⅠ, control groupⅡ, control group Ⅲ, 52 cases given joint inspection were seen as observation group. Positive conditions of the three groups were compared. Results Positive detection rate of the three control groups had no obvious difference, the difference was not statistic significant (P>0.05), positive detection rate of observation group was obviously higher than other 3 groups, the difference was statistic significant (P<0.05), express ratio of lymph gland and tumor diagnosed by ultrasound in control groupⅠ (67.31%, 92.31%) was higher than those of x-ray mammography in control groupⅡ (38.46%, 65.38%), express ratio of calcification and calcification with tumor diagnosed by x-ray mammography in control groupⅡ (42.31%, 32.69%) was higher than those of ultrasound in control groupⅠ(7.69%, 5.77%), the difference was statistic significant (P<0.05). Conclusion The combination of ultrasound, x-ray mammography and CT can significantly improve breast cancer positive detection rate and is worthy of wide application.