Based on Bailey's washback model, in respect of participants, process and products, the present empirical study was conducted to find the actual washback effects of the internet-based College English Test Band 4 (IB CET-4). The methods adopted are questionnaires, class observation, interview and the analysis of both the CET-4 teaching and testing syllabus. Through analysis, it is found that the IB CET-4 helps to establish the new computer and internet-based teaching model, to cultivate students' autonomous learning abilities, to improve students' ability for screen reading and keyboard writing as well as to urge colleges and universities to provide financial support to college English teaching and learning by constructing more internet language labs. However, overemphasizing practical ability, such as listening and speaking, leads to students' lack of spelling and grammatical knowledge.