Abstract: Objective To investigate cognition status of breast cancer and to provide evidence for health education on cancer prevention and treatment in Beijing community.Methods A population based cross-sectional study was conducted to investigate 2 952 women aged over 40 in a community of Beijing.Demography information,knowledge of risk factors of tumor and breast cancer and the source of tumor knowledge were collected with questionnaire in April 2008.Results There were 28.2% of the women having breast examination in professional clinic once a year and 23.1% of the women taking breast self-examination every month.There were 26.4% of the women knowing that overweight can lead to breast cancer more easily.Nearly half of the women knew genetic factor was one of risk factors of breast cancer.The main way of know-legdge for breast cancer was television(61.3%).The knowledge of breast cancer was related to age(χ²=12.386,P=0.002) and education(χ²=63.523,P=0.000).Conclusion The knowledge of breast cancer and its risk factor is very low among the women in community of Beijing.It is necessary to improve the understanding of breast cancer among the women through health education.