Objective：To comparatively explore the value of left ventricular end - diastolic maximal wall thickness（MWT）and anatomical parameters of left ventricular outflow tract（LVOT）for evaluating myocardial fibrosis in hypertrophic cardiomyopathy （HCM）by cardiac magnetic resonance（CMR）and propose a prediction model. Methods：Seventy-seven HCM patients who underwent CMR examination were retrospectively analyzed. CMR data included partial anterior mitral leaflets length and total anterior mitral leaflet length. During end - diastole and end - systole，the diameter of LVOT and the thickness of basal anteroseptum were measured. Additionally，left ventricular end - diastolic MWT was collected and the percentage of late gadolinium enhancement（LGE%）was analyzed. LGE% was used to assess myocardial fibrosis. Seventy percent of the samples selected randomly by statistical software were assigned to the modeling group（n=54）for establishing a prediction model of LGE% through univariate and multivariate analysis. The remaining thirty percent of the samples served as the internal validation group（n=23），and parameters of the echocardiogram of all patients were used as the external validation group to assess the accuracy of the prediction model. Receiver operating characteristic curves were plotted，and the predictive efficiency of the prediction model was determined by calculating the area under the curve. The sensitivity and specificity of the prediction model were also evaluated. Results：In the modeling group，multivariate analysis indicated that MWT was an independent predictor of LGE% with the linear equation LGE%=-10.009+0.832×MWT（r=0.466，P ＜ 0.001），while no anatomical parameters of LVOT were correlated with LGE%. In the external validation group，MWT measured by echocardiogram was highly positively correlated with MWT measured by CMR（r=0.856，P ＜ 0.001）. Additionally，the predicted LGE% values from both internal and external validation groups showed no statistically significant difference from LGE% . The accuracy of predicting LGE% ≥15% was 82.6% with MWT≥30 mm measured by CMR，and 81.7% with MWT≥25 mm measured by echocardiogram， respectively. Conclusion：When evaluating myocardial fibrosis in HCM，MWT has more predictive value than anatomical parameters of LVOT.