The invention relates to a method and a system for preventing a present network user terminal from accessing a testing carrier frequency cell. The method comprises the steps of Step 1, configuring a new location area code (LAC) for the testing carrier frequency cell on a radio network controller (RNC), and on a main storage controller (MSC), setting that a test terminal with a specific international mobile subscriber identity (IMSI) can access the testing carrier frequency cell and the present network user terminal can not access the testing carrier frequency cell; and Step 2, when the present network user terminal tries to log in the cell where the new LAC is located, the present network user terminal is forbidden to access. By the aid of the method, the interference caused by the present network user terminal to testing carrier frequency bands can be avoided.