Beware! You must be aware that beware and be aware are not the same!
Beware of your hands is a warning. It means that your hands are dangerous and you should be careful, or wary, around them. I can’t imagine why this warning is needed on Chinese buses, yet that’s where it appears.
Be aware of your hands is probably the intended message. To be aware means to have knowledge of something, or to think about it. Be aware of your hands is a polite way to say, “Don’t touch other people.” In America, we might say, “Please keep your hands to yourself.”