A method was studied to diagnose diesel misfire fault and ascertain the misfire cylinder number based on recognizing the vibration signal peak points of diesel cylinder head. Based on time-domain characteristics of waveform, seven criteria were described. The computer algorithm to identify time-domain waveform peak and locate misfire cylinder order number without top dead center signal was extracted from the 7 rules. The time domain waveform distribution change was analyzed under diesel misfire condition. The relative ratios of peak value were used on diesel misfire fault diagnosis and cylinder order number identification. The misfire fault identification rate based on this method was 100% in the experiment samples.