In this paper,we would like to suggest the use of network congestion optimizer which may have possibility to improve mobile-based foreign language classroom environment on the basis of our pilot experiments.In a foreign language teaching context,uploading and downloading a large volume of sound or video materials is very common in a wired computer classroom,or a so-called Computer-Assisted Language Learning(CALL)classroom.If we try this in wireless classroom settings with tablet or mobile computers,there is an issue of network congestion,which must be avoided by any means,because the trouble may make the students discouraged at the tasks.Since the introduction of tablet computers and one-to-one wireless classroom setting has been promoted by the Japanese government,this issue becomes more serious and real recently.This paper carried out an experiment using an English class in a Japanese university,where online training and downloading video materials were actually conducted and observed how the congestion change with the sue of the optimizer.The result was that the introduction of optimizer in addition to more reasonable standalone-mode Access Point(AP)is effective in reducing packet loss and raising communication speed.