Children's language development can reflect the developmental process of children's cognition and social emotions. The present study focuses on preschool children's conversational competence and narrative competence, aiming at exploring developmental features of preschool children's pragmatic competence through analyzing data from self-built oral language corpora using the INCA-A coding system and CLAN. Results show that with respect to using pragmatic indicators, frequency increases significantly with age in the dimensions of knowledge and language. In the language dimension, frequency is highest in the middle group and in the behavior dimension, frequency gradually decreases. Results are taken to indicate that preschool children's language competence improves continually, and gradually displaces the use of behavior-assisted language. Meanwhile, children can initiate conversation or discourse narration by using knowledge and language. Based on the findings, this study analyzes the development of preschool children's pragmatic competence at different ages within the framework of perlocutionary acts. Finally, corresponding educational suggestions are suggested.