Professor deletes me from Skype contact list after Skype interview and promise to give offer. Could this be a rejection? Recently, I had a Skype interview with a professor several weeks ago, and professor also promised me the PhD offer. My GPA is not high enough to meet the requirement of Department, but she said she would argue for me. After that, I also sent an email to professor and tried to talk about two academic questions, but no reply had been received. Recently, I checked my Skype and found professor has already delete the contact with me. And after I submitted the application, I also sent an email to inform the professor, no reply has been received either. So can I think it as a rejection?
No. I don't think you should assume that this is a rejection.


Deleting you from Skype does not sound unusual. If they added you for a specific purpose and don't intend to be contacting you regularly then they may just want to avoid notifications popping up all the time about when you are logged on.
Professors are busy. A lack of email reply, especially at this time of year when they may be about to leave for the holidays (depending on where you are in the world), may simply mean they not have got around to replying to you.
It's possible that the department you are applying to has strict procedures about job/studentship offers, such that the professor is not allowed to give you certain information until it has been formally confirmed by the school. Depending on the exact questions you asked, the professor may feel that they need to wait for the proper process before getting in touch with you again.


Assuming that you have gone through an official application procedure, which it sounds like you have, you will get official notification at some point from the department as to whether or not you have been successful. As I said above, be aware that might be a bit delayed due to the holidays. But I don't think you should assume one way or the other until you get the confirmation. 

Good luck!