Abstract: Objective To investigate the relationship between resting heart rate（RHR） and left ventricular mass index（LVMI） in patients with essential hypertension. Methods From January 2016 to December 2020, a total of 523 patients with essential hypertension who were first diagnosed or stopped taking antihypertensive drugs for more than 4 weeks from the First Affiliated Hospital of Fujian Medical University were enrolled. Five hundred twenty one normotensive patients in the same period were selected as the control group. Body height and weight, blood pressure and RHR of the two groups were recorded. Blood biochemical indexes and LVMI were determined. LVMI ≥115 g/m~2（male） or LVMI ≥95 g/m~2（female） was defined as left ventricular hypertrophy（LVH）. Results Compared with the control group, RHR and LVMI in the hypertensive group were significantly increased（68.9±10.4） vs（67.2±9.6） beats/min, t=-2.769;（99.9±22.1） vs（84.1±15.6） g/m~2, t=-13.432, both P＜0.01. According to RHR level, the normal blood pressure group and hypertensive group were divided into four subgroups: ≤60, 61-70, 71-80 and ＞80 beats/min. There was no significant difference in LVMI among the subgroups of normotensives（84.6±14.6）,（84.1±16.0）,（83.3±15.2）,（84.1±17.6） g/m~2, F=0.149, P=0.931, while significant differences existed in LVMI among the subgroups of hypertensives（106.6±20.4）,（101.3±22.8）,（93.5±19.4）,（97.7±24.2） g/m~2, F=8.059, P＜0.001. In hypertensive patients with RHR≤80 beats/min, LVMI gradually decreased with the increase of RHR. Multivariate linear regression analysis showed that after adjusting for other cardiovascular risk factors there was no independent correlation between RHR and LVMI in normal blood pressure group and RHR was independently associated with LVMI in patients with hypertension（β=-0.148, P＜0.001）. Stratified by RHR, further analysis showed RHR was independently and negatively associated with LVMI（β=-0.194, P＜0.001） in the hypertensive patients with RHR≤80 beats/min. However, there was no independent correlation between them in the hypertensive patients with RHR＞80 beats/min. After adjusting for other cardiovascular risk factors, multivariate logistic regression analysis showed that increased RHR was significantly associated with reduced risk of LVH in the hypertensive patients with RHR≤80 beats/min, and the risk of LVH in the hypertensive patients with RHR 71-80 beats/min was about one third of that in the hypertensive patients with RHR≤60 beats/min（OR=0.328, 95%CI 0.175-0.613,P＜0.001）. Conclusions RHR is independently and negatively associated with LVMI in the hypertensive patients with RHR≤80 beats/min. Hypertensive patients with RHR 71-80 beats/min have a lower risk of LVH.