Given the critical role of hydraulic blasting in practical blasting engineering and the fundamental importance of crack propagation studies for revealing blasting mechanisms, this research focused on investigating the crack propagation evolution law in water pressure blasting through model experiments. Small-scale cement mortar specimens were prepared for blasting tests, with high-speed photography employed to capture dynamic fracture processes. The study systematically analyzed surface crack characteristics, quantified crack propagation velocities, and examined the stress field distributions in the specimens during hydraulic blasting operations. The experimental results indicate that the water-coupled charge structure generates 5 extensive surface cracks on the test block after blasting, whereas the non-hydraulic structure produces only 1 primary fracture, clearly demonstrating the superior fracturing effectiveness of hydraulic blasting technology. Experimental measurements reveal that the water-coupled charge specimen initiates cracking 0.112 ms earlier than its non-hydraulic counterpart, achieving a peak crack propagation velocity of 645.85 m/s. This represents approximately a 2.5-fold increase over the non-hydraulic structure′s performance, with a corresponding substantial enhancement in average propagation speed. Lateral tensile stress predominantly governs crack propagation on specimen surfaces, with the water-coupled charge structure exhibiting consistently higher surface strain magnitudes than non-hydraulic configurations throughout the fracturing process. These findings establish crucial theoretical foundations for optimizing hydraulic blasting techniques in engineering practice.