准备考研英语可以用以下几种英语表达：

preparing for the postgraduate English exam

studying for the postgraduate English exam

I am preparing for the postgraduate entrance examination

I am studying for the postgraduate entrance examination

I am hitting the books for the postgraduate entrance examination

I am diligently preparing for the postgraduate entrance examination

这些表达都准确地传达了准备研究生入学考试这一概念。根据具体的语境，可以选择合适的短语来表达自己的准备情况。例如，在和朋友聊天时，可以使用“I am hitting the books for the postgraduate entrance examination”来表示正在努力学习；在与老师交谈时，则可以使用“I am diligently preparing for the postgraduate entrance examination”来展示自己的勤奋和努力。