Rules in China are often changing and some schools want different things than others
The school is NOT being unreasonable by requesting to see your original
Is there anyway you can get it mailed to you?
If you are going to provide a copy then it needs to be authenticated - otherwise the school could accuse you of providing them with a fake degree copy
It is becoming more common in parts of China for employers to ask to SEE the original
If you don't have it, I suggest you get it
It may take time but if you talk to the school and tell them you have asked for it to be mailed, they will likely believe you and it shouldn't stop them from employing you