Don't worry, the interview of Oxford's is much easier than that of Cambridge's. They simply ask you things regarding your background (your work experience, your team work experience), it's more like chatting with the interviewer...
Cambridge interview is very tough. I was interviewed by two professors, and they had challenging questions from the beginning. However, all the questions are related to your background. so find your weakness, and prepare well. good luck.
Thank you all for your kindness. I am now still thinking more deeply about myself, who I am, what I want, and what I should do. I never analyzed myself like this before. Actually, the application itself can make me think. Now I know that a MBA could shape me.
Whether or not I am admitted, I appreciate this experience. And you Oxford or Cambridge fellows, thank you very much. You are impressive.