The Sachun Interchange Intersection which is T type will be moved toward Jinju city from present location as the Namhae Expressway is enlarged. The new Sachun Interchange Intersection will be built as the grade separated interchange constructing the through road as the underpass. The start of the underpass begins in the middle of a curved section and the longitudinal grade of the underpass is too steep as a bridge located right after the underpass. Thus, there are serious problems except that the cost is high. The purpose of this study is to suggest a practical and efficient alternative which improves traffic operation at the intersection. Two alternatives are conceived, the one is constructing a at grade intersection and the other is connecting the new tollgate to the present intersection. Among the alternatives, the at grade intersection is judged to be the best because the at grade intersection operates traffic efficiently/safely and the cost is low. Moreover, the at grade intersection make it possible to change the present intersection to the diamond type interchange which increases the accessibility and safety of the traffics of surrounding areas.