A method for detecting a typical defect area on a disc track includes the following steps. Firstly, a source signal is provided. Then, first and second signals are generated according to the source signal. The first and second signals are held at the peak level of the source signal and respectively decreased at first and second drop rates. Then, first and second threshold values are subtracted from the first and second signals to generate first and second slice signals, respectively. Afterwards, the source signal is compared with either the first slice signal or the second slice signal. When the first slice signal is larger than the source signal, a typical defect signal is changed from a first level to a second level. Whereas, the typical defect signal is changed from the second level to the first level when the second slice signal is smaller than the source signal.