Currently, the drilling and blasting method remains the primary excavation technique for underground powerhouses in hydropower stations across China. Blasting excavation inevitably induces damage to the surrounding rock of underground powerhouses, leading to the degradation of its mechanical properties, reduction in integrity and strength, and potentially triggering latent engineering hazards. Consequently, the accurate prediction of the blast-induced damage zone in the surrounding rock constitutes a critical factor for ensuring the safety of drilling and blasting construction in hydropower station underground powerhouses. Accordingly, this study employed a comprehensive approach integrating field tests, numerical simulations, and theoretical analysis to investigate the characteristics of blast-induced damage in surrounding rock during bench blasting for underground powerhouses, and a prediction model for the damage depth in the sidewall surrounding rock was proposed.