From the standpoint of the social constructionalism, the processes of the peer interaction in the group play activities were observed during three years longitudinally. The video-taped data for this study were collected in a microethnographic approach of peer plays, i.e., social pretend play, associative play, and cooperative play et al., in the natural setting of the Japanese nursery school.This study contained the microsociolinguistic analyzes of 200 videotaped peer interactive episodes of each age group of 3 to 5 years old.The main purposes of this study were to clarify the interactive nature of the peer play, and the relationship between the processes of the peer interactive activities during the peer play and the constructional processes of the peer groups.Two older age groups (4 and 5 years old) were able to successfully enter into one of the ongoing peer play episode. They could also negotiate the playing activity or share the script (theme of the peer play) with each other in their role play. Therefore, the train of their play episode were more longer than the younger one. Through the microsociolinguistic analyzes, the following findings were obtained. Two older age groups have used a wide variety of access strategies, i.e., entering strategies to accessing to an ongoing play episodes, and also used effective strategies for sharing and maintaining the role play activities or script in the episode. The youngest age proup (3 years old) children could not use the above effective strategies.From the longitudinal data, it was found that the interrelationship among the peer members of the two older age groups, especially 5 old age group, were more sophisticated and highly organaized, and therefore, the structural nature of their age groups were medium of their social interactive activities in the peer plays.