The purpose of this study was to clarify the effects of the environmental education system focusing on the knowledge, attitude and practice in relation to environmental education to the students in Mokpo middle school. The study is accomplished by the survey which includes a total of 268 inquiry lists sampled from four groups of the middle school, one of which composing of two middle schools having the environmental curriculum, hereafter referred as 'the case group' and the other group of two middle schools without the curriculum, hereafter referred as the 'the control group'. From the results of the average scores on the environmental knowledge, attitude and practice between the two groups, the case group showed better knowledge scores than the control group (p<0.05). The case group with environmental education were relatively high to the control group without environmental education to the attitude(p<0.05), and did not showed signifiant differences in the environmental practice. From the results of stepwise multiple regression analysis, the factor affecting the environmental knowledges was the interest in the environment problems (R2=0.130), economic status, academic achievement and the necessity of environment conservations in order. The factor most affecting to environmental attitude and practice were the interest in environmental problems of the parents.