Abstract: AIM To investigate the relationship between plasma homocysteine, heart rate variability (HRV) and severity of coronary artery heart disease (CAD). METHODSTwo hundred and seventy-eight patients with CAD confirmed by coronary angiography (CAG) were divided into three groups by Gensini scoring: minimal group (n=76), moderate group (n=109) and severe group (n=93), and 61 non-CAD patients were assigned to control group. Plasma homocysteine was detected, 24-h ambulatory electrocardiogram was performed and the index of HRV was recorded. The results were analyzed and compared. RESULTSPlasma homocysteine levels increased with the Gensini scores and a significant difference was found between minimal, moderate and severe groups (P<0.05). The index of HRV had a decreasing trend with the increasing extent and severity of coronary artery lesion (P<0.05). Plasma Hcy level and the index of heart rate variability were associated with severity of CHD. Hcy and HRV were risk factors for coronary artery disease. CONCLUSIONHRV and plasma Hcy are closely related to the severity of CAD and have some value in predicting the severity of CHD.