Background: Myocardial bridging (MB) was associated with various arrhythmia forms like supraventricular tachycardia, ventricular tachycardia, atrioventricular conduction block, and sudden cardiac death. However, the relationship between MB and preoperative atrial fibrillation (AF) remains unknown. Hypothesis: The presence of MB increases the risk of preoperation AF in adult patients with obstructive hypertrophic cardiomyopathy (OHCM). Method: We recruited 968 consecutive patients with OHCM who underwent surgical myectomy at Fuwai Hospital in Beijing, China, from January 2015 to December 2019. Patients were divided into two groups based on invasive coronary angiography: patients with MB group (N=144) and patients without MB group (N=824). Result: Patients with MB were much younger (43.6 vs. 48.8 years, p < 0.001), more likely to have palpitation (37.4% vs. 25.5%, p = 0.003), had a lower body mass index (24.8 vs. 25.7 kg/m2, p = 0.009), a lower incidence of hypertension (14.6% vs. 27.9% p = 0.001), a higher prevalence of AF (26.4% vs. 11.5%, p <0.001). After adjusting for age, sex, left atrial diameter, and LVOT gradient, multivariate logistic regression analysis revealed that the presence of MB was independently associated with AF (Odds ratio [OR] 3.73; 95% Confidential interval [CI] 2.32-5.98, p < 0.001). Furthermore, we conducted a LASSO logistic regression to select variables associated with AF from patients with MB subgroup, and five non-zero variables were included in the multivariate logistic regression model. The results indicated that compared to patients with MB on the middle left anterior descending coronary (LAD), those with MB on the proximal LAD had a higher likelihood to develop AF (OR 4.22; 95% CI 1.40-12.68, p = 0.01). Moreover, MB compression (OR 1.04; 95% CI 1.04-1.08, p = 0.013) and MB length (OR 1.06; 95% CI 1.004-1.11, p = 0.034) were independently associated with a higher prevalence of AF after adjusting for age and left atrial diameter. Conclusion: The presence of MB and its location, length, and compression degree were independently associated with an increased risk of preoperative AF in adult HOCM patients, which suggested that whether MB needed surgical treatment during septal myectomy should be considered.