This paper is a research in the second Language acquisition (SLA) with its focus on the role of input, interaction and output in the development of oral fluency in the EFL context from both a theoretical point of view and a case study. Two instruments were used: tests of oral fluency and face-to-face interviews. The findings showed that non-native oral fluency could be obtained through efficient and effective input, interaction and output in EFL while on the other hand they suggested answers to the question why most Chinese English learners failed to speak English fluently, namely lacking effective input and output, having no real need for interaction, attaching too much importance to language forms and written tests.