For perpendicular magnetic recording by a bi-layered main-pole head which shows an excellent linearity, the performance of PRML system combining partial response (PR) system with maximum likelihood (ML) decoding is studied. The bit-error rate of the PRML system using a PR(1,1,0,0,0,0, − 1, − 1) system is obtained by computer simulation and compared with that of the conventional PRML system. It is shown that our PRML system exhibits better performance than the conventional PRML system in high density recording.