A method for determining the writing power of data recording devices. First, the inner circle and outer circle of recording media are processed with optimum power calibration (OPC) to obtain an inner circle optimum writing power and an outer circle optimum writing power respectively. The writing power is determined according to the inner circle optimum writing power, outer circle optimum writing power, and/or the time of write speed is raised from the minimum write speed to the maximum write speed of the data recording device.