Today, children's literature given the concept of childhood, has gained a special status in the studies of humanities. Children's poetry is one of the branches of this type of literature. Naturalistic themes have the highest frequency among the themes of children poems in two countries. The population of this research consists of collections that have been published from 1921 to 2011. Children's literature was born in England in the eighteenth century and before that the first didactic books for children had come into existence in England. In addition, due to industrial growth, the emergence of the new middle class and expansion of formal education the UK was pioneering among Europe and the world countries. Therefore, to find the roots of the formation of children's literature should be referred to the UK. Therefore, in this paper Britain children's poem has been selected to be compared with Iranian children's poem so that by revealing the similarities and differences one can deal with the pathology of poems for children in Iran and to detect shortcomings and strengths and present some guidelines that be helpful for children and young poets as well as critics and researchers in this field.