Abstract: In order to study the influence of underground blasting mining on open-pit slope in the process of combined open-pit and underground mining, a simplified model of underground blasting excavation under the most dangerous working condition is established by using finite element simulation software ANSYS/LS-DYNA. The damage expansion process of rock mass from blasting source to slope and the attenuation law of blasting vibration velocity in the model are analyzed. On this basis, the simulated data are verified in the field test. The result show that the local lower stope is blasted with a theoretical maximum charge quantity of 60 kg without considering the effect of elevation amplification, the actual vibration velocity of the open-pit slope will exceed its safety allowable threshold of 10 cm/s, affecting the safety and stability of the slope. In the process of underground blasting mining, the damage first occurs in the rock mass near the blasthole, and with the propagation of the stress wave, the damage occurs at the foot of the slope closest to the blasting source, and then extends along the slope surface, and gradually extends to the whole slope. However, the peak vibration velocity of blasting in rock mass decreases with the increase of blasting source distance, and the attenuation velocity first attenuates quickly and then slowly, but the vibration velocity appears magnifying effect at the slope surface near the peak slope. And the damage evolution process from the blasting source to the slope surface corresponds to the attenuation law of vibration velocity. In order to ensure the safety and stability of open-pit slope, the maximum charge quantity of underground mining should be controlled within 40 kg in practical engineering. The research results can provide reference for the safety production of similar mines.