In view of the problem of the unclear influencing factors of rock-breaking efficiency in underwater vibrational impact rock-breaking technology,the impact effects of various factors on rock fragmentation are investigated.By the finite-discrete element method(FDEM)and coupled Eulerian-Lagrangian(CEL)method,a three-dimensional numerical model of underwater vibrational impact rock-breaking built in ABAQUS software to simulate the rock-breaking process and study the influence of different factors on rock fragmentation.The results indicate that the presence of hydrostatic pressure promotes a transition from brittle to ductile states during rock failure.Increasing the static pressure applied by the cutterhead significantly enhances its penetration capability.However,excessively high pressure exacerbates stress oscillations,necessitating optimized load combinations on the basis of engineering practice.Higher rock compressive strength increases the difficulty of cutterhead penetration.A clear negative correlation exists between water depth and penetration capability:in shallow water(5-6 m),the constraining effect of hydrostatic pressure on rock strength is weaker,resulting in lower energy loss of the cutterhead,whereas in deep water(8-9 m),penetration efficiency decreases.The penetration depth of the cutterhead exhibits a characteristic of first increasing and then decreasing with higher vibrational frequency.