Objective: To investigate the relationship between cardiac magnetic resonance(CMR) myocardial strain rate (SR) parameters of left ventricular diastolic function and the risk of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM). Methods: A total of 160 HCM patients and 50 healthy control subjects who underwent CMR were enrolled. Radial strain rate (RSR), circumferential strain rate (CSR) and longitudinal strain rate(LSR) of left ventricle (LV) by CMR were measured. Risk stratification of SCD by 2014 European Society of Cardiology(ESC) and the 2020 American College of Cardiology/American Heart Association (ACC/AHA) guidelines were performed in patients respectively. Differences in diastolic function between high-risk and low-risk groups under the same guideline were compared with t test and one-way ANOVA was used to compare diastolic function between subgroups based on two guidelines. Linear regression analysis was performed to analyze the association of commonly risk factors in guidelines and diastolic function. Results: The absolute value of diastolic SR of LV in HCM was significantly decreased when compared with those of control subjects (RSR: -1.27 ± 0.60 vs -2.40 ± 0.59, CSR: 0.71 ± 0.24 vs 1.22 ± 0.25, LSR: 0.52 ± 0.24 vs 0.89 ± 0.20, all P<0.05). There were significant differences in diastolic RSR and CSR among HCM different phenotypes (all P<0.05). Patients with high SCD risk (n=27) according to the 2014 ESC guidelines had significantly lower diastolic RSR(P<0.05) than those with low SCD risk,while had no difference in CSR and LSR. Patients with high SCD risk (n=92) according to the 2020 ACC/AHA guidelines had significantly lower diastolic SR(RSR, CSR and LSR) (all P<0.05) than those with low SCD risk. The diastolic SR in patients with low SCD risk by 2014 ESC but high SCD risk by ACC/AHA were similar with patients at high risk based on both guidelines, and were significantly lower than that of patients at low risk in both guidelines. Among the four major risk factors, the absolute value of diastolic myocardial SR were significantly decreased in the group which had higher maximum left ventricular wall thickness (≥30 mm) and late gadolinium enhancement/left ventricle mass (≥15%), and LV diastolic function was severely impaired. Maximum left ventricular wall thickness and late gadolinium enhancement/left ventricle mass both had significant association with diastolic myocardial SR (correlation coefficient r were 0.48/0.35 in RSR, -0.42/-0.31 in CSR, -0.37/-0.16 in LSR, all P<0.05). Conclusions: SR of LV myocardial by CMR is significantly reduced in patients at high risk of SCD, and is correlated with some risk factors, which may serve as a new biomarker to assist the stratification of SCD risk.