The multilevel disc, which uses the signal waveform modulation method for modulation and recording, employs the partial response maximum likelihood detection techniques for the readout channel recovery. With improving the recording density, the complexity and nonlinearity of the optical disc channel modeling will also increase. Therefore, a optimized design method of the partial response polynomial and the corresponding equalizer design were introduced to solve it. By finding the critical frequency point between signal frequency band and noisy frequency band in the power spectral density curve of the disc readout signal, the optimized parameters of the partial response polynomial and the partial response equalizer were designed, thus effectively improving the optical readout signal to noise ratio, reducing the error rate of the signal recognition. And this method can also be applied to the partial response maximum likelihood detection system of bluray and other highdensity baseband transmission channel.