Underwater drilling blasting is a widely used technique in aquatic engineering construction. The shock waves generated during blasting exhibit instantaneous intensity and rapid diffusion. Raising significant concerns about their impact on aquatic organisms and ecosystems. Drifting larvae, due to their small size and limited swimming escape capacities, are vulnerable to underwater blasting shock waves. This study investigated grass carp (Ctenopharyngodon idella) larvae, a dominant species in the upper Yangtze River, through field blasting experiments (ingle-hole charge:26 kg a; total charge: 300 kg), combined with laboratory cultivation and histological analysis, to determine damage thresholds and mechanisms. Results indicate that when the peak shockwave pressure decreased to 0.383×105?Pa (at 500 m distance), instantaneous larval mortality showed no significant difference from the control group (p>0.05p>0.05). After 4 days of laboratory cultivation, cumulative mortality approached control levels, establishing 500 m as the ecological safety distance. Histological analysis revealed distance-dependent liver damage, with kidney injury identified as the primary cause of delayed mortality. The ≥200 m group retained largely intact glomerular structures, but a 18.9% cast formation rate persisted at 300 m, indicating sublethal damage risks. Muscle damage showed only weak correlation with mortality, confirming its non-lethal role. Protective strategies such as spatiotemporal avoidance (based on species sensitivity) and bubble curtain technology (achieving 60–80% pressure attenuation) were proposed. This work quantifies damage thresholds, clarifies injury mechanisms, and provides scientific foundations and technical solutions for ecological protection in aquatic blasting projects.