The present invention relates to a system and method for issuing an authentication key for authenticating a user in a CPNS environment. The system comprises a user terminal, a gateway and a CPNS device. The user terminal is equipped with a short-range wireless communication function, requests the gateway to register terminal information including an ID and password, encrypts the terminal information including the ID and password using the password, transmits an authentication request signal including the encrypted terminal information to the gateway, and receives an authentication key generated by a CPNS device. The CPNS device stores the terminal information, performs user authentication by decrypting the encrypted terminal information in response to the authentication request, generates an authentication key for the CPNS when a user is authenticated, encrypts the generated authentication key using the password, and transmits the encrypted authentication key to the user terminal through the gateway.