This invention discloses a method for accessing the core net by user terminals under the shared carrier frequency mode including: registering one or more than one PLMN marks and a CS/PS network corresponding to each PLMN mark in a user terminal, also including: a, the terminal selects a CS or PS network corresponding to the PLMN mark, b, the user terminal initiates an access request to the CS or PS, c, the terminal receives the access response of the network side to judge if the the access is successful, if so, it registers the PLMN mark of the current CS/PS network, if it fails, it selects another CS/PS network corresponding to the PLMN mark then returns to step B. |