Objective：To determine the prevalence of q wave in avL，prescribe its characteristics，and evaluate the correlation between the q wave in avL and organic heart disease（OHD）verified by gated single-photon emission computed tomography myocardial perfusion imaging（SPECT-MPI）and coronary angiography（CAG）or coronary computed tomography angiography（CCTA）in the patients with complete left bundle branch block（CLBBB）. Methods：A total of 1 882 CLBBB patients were initially involved in the study，and the results of SPECT-MPI，CAG and CCTA were collected. The prevalence，duration and amplitude of q wave as well as the duration and amplitude of QRS complex in avL were measured，on which the correlation between q wave and OHD were analyzed. Results：In this study，157 patients were involved finally，and 122 of which（77.8%）were confirmed with OHD by SPECT-MPI，CAG and CCTA. Septal q waves were present in 56 of the 122 OHD patients（45.9%）［OHD（+）q（+）group］. Specificity and positive predictive value of q wave in avL for OHD were 97.1% and 98.2% respectively. Comparing with the CLBBB patients in OHD（+）q（-）group，the CLBBB patients in OHD（+）q（+）group have larger end diastolic volume（EDV）（P＜0.001）and end systolic volume（ESV）（P＜0.001），but lower left ventricular ejection fraction（LVEF）（P＜0.001）. Scatter chart and correlation analysis showed no significant linear correlations between the duration，amplitude，areas of q wave and the left ventricular ESV，EDV and LVEF verified by SPECT-MPI. Conclusion：Occurrence of q wave in avL in CLBBB patients indicates serious left ventricular disease，but there is no linear correlation between the characteristics of q wave and the severity of left ventricular disease.