Thanks a lot for everyone's replies, and apologize that I don't know how to express my thanks to each of you.
I notice that most of you mention that I should listen to more English programs, actually I listen to VOA and watch a lot of U.S. drama series everyday. But most of the time, I still need to depend on the subtitles, especially the teleplay, because they speak too fast and no more to say the slangs. What's more, because of the limits of my univ, I don't find too much students to talk with me in English, so I don't have many time to practice my English,
So could you give me some advice about my hearing and how can I find someone to talk with me? By using the Facebook?