Objectives: This study examined the life style differences of middle school students among in Korea, China and Japan and analyzed the factors influencing on the perceived health. Methods: The data of 1,390 students aged between 14 years and 16 from three countries collected between in November, 2008 and January, 2009 and analyzed the data using $x^2$-test, ANOVA-test and logistic regression analysis in SPSS Win 12.0. Results: Korean students spent more time on study and mobile phone use than Japanese, and more time on TV computer game than Chinese students. In addition, Korean students had a higher percentage in skipping breakfast and in not exercising than the other two countries. Overall, students who went to bed before midnight, having breakfast or doing exercise had better perceived health. Conclusions: The policies on health education should be conducted at a national level in order to improve their unhealthy life styles of Korean middle school students.