I'm tying to convert a MFRC522 arduino chip to an USB device so as to use it natively on windows (with a cli or software) and without an Arduino. I don't know if I was clear (sorry for my bad english). Can anyone help me to do this.
No, you can't do that because you need some mediation between the RFID reader and the PC USB port.
You don't have to use Arduino, but you do need a processor to "translate" the information from the reader and some hardware to speak to USB.