Abstract: Objective To investigate relationships between knowledge and corresponding behaviors of dietary and physical activity (PA) among primary and middle school students in Nanjing city and to provide references for health education and intervention on obesity among the students.Methods Totally 10 124 students were selected from 48 schools in Nanjing municipality with multi-stage proportionate cluster random sampling and investigated with a self-administered anonymous questionnaire survey in September 2013 and 9 426 questionnaires were received at last.Results Among the students,the proportion of students knew "PA could lose weight","television viewing or computer use could lead to overweight","soft drinks could lead to overweight",and "western fast food could lead to overweight" were 81.1%,33.0%,74.2%,and 82.8%;the proportion of physical inactivity,prolonged sedentary time,excessive intake of soft drinks,and excessive intake of western fast food were 49.9%,4.4%,10.4%,and 9.5%,respectively.The knowledge rate of dietary and PA and the prevalence of unhealthy life behaviors differed significantly among the students with different grade,gender,parental education,and family population (P<0.05 for all).Logistic regression analyses showed that the students being aware of the knowledge about the four unhealthy behaviors had low proportion of physical inactivity (odds ratioOR=0.785),prolonged sedentary time (OR=0.603),excessive intake of soft drinks(OR=0.566),and excessive intake of western fast food (OR=0.425).Conclusion Awareness of obesity knowledge has positive influences on students' life behaviors and specific health education on obesity should be promoted among the students.