This paper presents a corpus-based analysis of the nature of spontaneous storytelling activity in daily conversation. Based on both the structural and interactional views of oral narrative, it proposes to add another perspective, arguing that conversational storytelling is a three-dimensional construct, with narrative, interactive and cognitive functions performed simultaneously in the context of social communication. The study has recorded 15 pieces of casual talks by 11 adult native speakers of Chinese and extracted 87 stories altogether. From the data, we observe that in the process of conversational narratives, (1) narration is achieved interactively, with the narrative sequence, story structure and even tellership all framed by communicative needs; (2) interactional activities, such as self-image building, interpersonal work and social-cultural practice are engaged in; (3) intersubjective social cognition is also achieved as personal experience becomes shared and cooperatively interpreted.