As doctors and patients communicate with each other during medical interactions, they are bound to interrupt others and be interrupted as well. By treating these interruptions as interactional strategies which link social structure to social interaction, we display how the medical interview is characterized by a moment-to-moment struggle that mirrors and largely sustains the institutional authority and status of doctors.In this paper, this unbalanced power relationship will be analyzed with linguistic theories, methods and practices. It examines the use of interruptions, their frequencies of occurrence and the social significance in the doctor-patient conversation through quantitative and qualitative analysis of linguistic data. The interruption will be studied from three dimensions: their consequences,occurring manners and the occurring reasons behind that. The interruptions occur more often in the doctors discourse than that in the patients, and the causes behind their interruptions are different respectively. The data are all drawn from the outpatient departments. The analyses of the data show that most of the interruptions in the doctors discourse are closely related to power. In an attempt to combine the linguistic data with the power concept, this paper tries to incorporate the doctors and patients speech of different characteristics with several important concepts in linguistic pragmatics: "face", "politeness rules", "world", "corporative principles",etc.