A method of identifying a wafer serial number is provided. First, a wafer having a wafer serial number is provided. Second, an identification procedure is carried out to identify the wafer serial number by means of multiple identification recipes thereby obtaining multiple digit results which correspond to the multiple identification recipes and a specific digit in the wafer serial number. The multiple digit results include at least two of a successful result and an unsuccessful result. Then, the wafer serial number is determined in accordance with the multiple digit results.