Abstract: To study the characteristics of ultrasonography and mammography in the treatment of breast cancer in situ with early infiltration and to evaluate its diagnostic accuracy. Methods: The results of mammographic and ultrasonic diagnosis of 40 patients with breast cancer in situ with early infiltration were contrasted. Results: In the 40 patients, the sign of breast cancer by mammography was found in 28 (70%), benign tumor in 7 (17.5%) and no tumor in 5 (12.5%). The ultrasonographic indication of breast cancer was seen in 13 (32.5%) of the 40 cases, benign breast tumor in 10(25%) and no tumor in 17 (42.5%). Tumor- free cases were not found after the examination by mammography plus ultrasonography. Conclusion: In the diagnosis of breast cancer in situ with early infiltration,the coincidence of mammography and pathology was higher compared to ultrasonography of the breast. The examination by mammography combined with ultrasonography can reduce the missed- diagnosis rate of the early breast cancer.