The purpose of this study is to investigate the functions of prefrontal lobe on the formation of conservation scheme of elementary students. In this study, 107 students of 4th to 6th grades were selected from the elementary school in Seoul area. As to the research,4 items for conservation logic test from GALT test sheet were used. The planning ability, inhibiting ability and reasoning ability were measured for the prefrontal lobe functions. About 30% of 4-6 grade students did not have volume conservation logic skills. The formation of conservations was not linear. Inhibiting ability was significantly different in level of conservation. And, conservation logic skills were significantly correlated with cognitive variables. Reasoning ability was significantly explained about 10% of the conservation logic in 4-6 grades.