A method for automatically switching subscriber mode through identifying IMSI includes, when a cell phone is turned on, determining if a first IMSI is consistent with a pre-stored second IMSI. If the first IMSI is determined to be consistent with the second IMSI, the cell phone enters a subscriber mode corresponding to the second IMSI. If the first IMSI is determined to not be consistent with the second IMSI, the first IMSI is matched with a third IMSI of an IMSI list pre-stored in the cell phone; when the first IMSI is determined to be consistent with the third IMSI, the cell phone enters a subscriber mode corresponding to the third IMSI. Thereby, the cell phone quickly and efficiently completes identifying an IMSI and automatically switches subscriber mode.