A mobile communication system selection is disclosed. A method for selecting a mobile communication system of a portable terminal includes driving a first timer; checking whether a Mobile Country Code (MCC) of a region where the portable terminal is located is obtained by searching for a network until the first timer expires; when the MCC is obtained before the first timer expires, storing the obtained MCC to a previous MCC list; performing a first checking operation for checking whether the obtained MCC belongs to a list of countries supporting only a first mobile communication system; and obtaining a service of the first mobile communication system by searching for only the first mobile communication system when the obtained MCC belongs to the list of the countries supporting only the first mobile communication system.