A method for performing optimal recording power calibration (OPC) on a recording medium, such as a DVD-RW, is characterized by flagging the address of the last test data. The method enables a recording position of the last test data to be quickly retrieved by recording position information of a power calibration area, in which the last test data is recorded, and indication information (such as a flag bit) indicating the recording position information is the last test data, in a specific area of the recording medium, such as the second field (field 1) of the format 1 RMD (recording management data). Such a method shortens the processing time prior to the OPC, and does not require the recorder to employ registers to determine the address of the last test data.