Abstract: Objective To study the expression of apoptotic protease activating facter-1 （Apaf-1） and Ki-67 in breast cancer tissues and normal breast tissues， and to investigate the clinical significance of the two proteins. Methods From January 2014 to December 2015， paraffin blocks of 60 cases of breast cancer tissues and 30 cases of adjacent normal tissues were enrolled in this study. The expressions of Apaf-1 and Ki-67 were detected using immunohistochemical EnVision method. The relationship between the two proteins，as well as the relationship of them with clinicopathological factors（age, tumor size, lymph node metastasis, clinical stage and body mass index） was also analyzed. Results The positive rate of Apaf-1 in breast cancer tissues was 21.7% （13/60）， which was significantly lower than that in adjacent normal tissues （70.0%， 21/30）， and the difference was statistically significant （P<0.05）. The positive rate of Ki-67 in breast cancer tissues was 73.3% （44/60）， which was significantly higher than that in adjacent normal tissue （11/30， 36.7%）， and the difference was statistically significant （P<0.05）. Apaf-1 and Ki-67 were not related with age， body mass index（P>0.05）， but with tumor size， lymph node metastasis and clinical stage （P<0.05）. The expression of the two protein in breast cancer tissues was negatively correlated （r=-0.413，P=0.018）. Conclusion In breast cancer, Apaf-1 expression was decreased but Ki-67 expression was elevated. Apaf-1 and Ki-67 play an important role in the development and invasion of breast cancer，and may be used as a marker to diagnose the breast cancer.