be preparing for是正在为....做准备,如:
I am preparing for the exam. 我正在为考试做准备。
be prepared for 是为......做好准备,如:
we should be prepared for the exam. 我们应该为考试做好准备。
be prepared for 对 ... 有所准备
We should be prepared for any contingency. 我们应该对任何应急情况有所准备.
来自《现代汉英综合大词典》
be preparing for 正在为.....做准备
Seaside resorts such as Blackpool and Brighton are preparing for a tourist invasion.
像布莱克浦与布赖顿这样的海滨胜地正为游客的大批涌入做准备。
来自柯林斯例句