The flow theory is a new way of understanding motivation, first proposed by Csikszentmihalyi. If language learning can produce such flow experience, learning would become optimal experience, which is a heightened level of motivated task engagement, leading to improved performance on a task. Through the investigation of students' perception of flow in playing four different online computer games, the study finds that: 1) Free online games with clear walkthrough steps can motivate EFL students, and flow occurs in the EFL classroom; 2) Free online games offer a potential for language learning although MOO [Multi-User Domain, Object Oriented] may need more orientation because of its pure text interface; 3) The balance between challenge and skills plays an important role in students' perception of flow. Since there is not much research on flow in EFL classrooms, this study provides one application of flow theory in an EFL context, and advocates the use of computer games in English learning.
