The partial response maximum like-hood (PRML) can not be directly used for the signal waveform modulation (SWM) multi-level (ML) recording,because in SWM ML,the signal after time recovery does not respond to a symbol sequence. An adaptive level detection method based on minimum Euclid distance is proposed. The Euclid distance between the actual waveform and reference waveform is employed for the level detection. Adaptation can make the set reference waveform approach the actual waveform. The protection mechanism can prevent the case that the reference waveform greatly deviates from the actual. Experimental results show that,without adjusting parameters,this detection method can achieve a low level error ratio,which is less than 2×10-4,for different disk batches. It also has capability for disks with defects. Using this level detection method,the playback system realizes stable and continuous playback of high definition video.