The study aims at exploring the relationship of children from the same age group and that of children from different age group in relation to the differences in their physical environmental elements through play of forest. From the analysis of results, it can be seen that in the group of children from different age groups, the differences in their physical performances leads to the cultivation of a yearning and desire to play as well as to give help. On the other hand, in a group of children of the same age, when the differences in their physical performance is realized, it leads to jealousy and impatience among the children. But because of the characteristics of the forest, children can look for other play without other children within the boundary of the forest. These Characteristics are (1) Forest offers a place where children freely decide what to play by themselves. (2) Because the insects and plants in which children are interested, exist in the forest, it has the diversity and the complexity which do not remain in the fixed method of play. So forest’s play spreads according to the children’s infinite imaginative power. Therefore, it can be said that a child’s performance is greatly influenced by the differences in age interaction as well as differences in physical performance. While forest exposes the differences of age and physical performance in children, it also promotes and develops children’s play and relationship.