A block code error correcting system is used in a compact disk reading system to increase the decoding capability of the compact disk reading system. The system includes a data slicer, a data bit to channel bit modulation pulse width determinator, a demodulator, an erase address detector and an error correction code (ECC) decoder. A pulse width of an eight-to-sixteen modulation (EFM+) signal is detected to thereby produce an erase control signal when the pulse width of the EFM+ signal is in a predefined window or is an illegal pulse width. A codeword corresponding to the EFM+ signal is set as an erasure, and accordingly an erase address is produced.