The purpose of this study is to describe and analyze the mental rotation of young children. The study addressed the observation of young children construct a solid and imagine a solid from its unfolded plane. First subject is making solid its same color surfaces facing each other. 5 years children were tend to construct a solid using same color. (58.5%) 6-7 years children were tend to construct a solid using its unfolded plane. (78%,64.7%) Second subject is making a solid from its unfolded plane using mental rotation. 5-6 years children scored, 28.3%, 26.6%, to imagine a solid from its unfolded plane. 7-years children scored 61.6%, to imagine a solid from its unfolded plane. The result indicate that at first young children change how to make a solid from using surface as its looks, to using unfolded plane. Mental rotation of young children from 2-D (unfolded plan) to 3-D (solid) develop with using construct a solid from its unfolded plane and they will get image of making a solid in their sense.