Aiming at the ultimate bearing capacity of pile end rock in the single row pile foundation of underly? ing cavity bridge，based on the punching shear failure theory of pile end rock of single row pile foundation for under? lying cavity bridge，the failure mode of pile end rock of single row pile foundation of underlying cavity bridge is as? sumed. The calculation method of the side area of the overlap part of the punching shear under each pile is obtained by using the spatial surface integral. Further considering the relationship between the overlap area and the reduction of the bearing capacity of the pile end rock，a calculation method of the ultimate bearing capacity of the pile end rock of the single row double pile and the single row three pile foundation of the underlying cavity bridge is proposed. The rationality of the method is verified by experiments. And the influence of pile spacing L on the ultimate bearing capacity of rock strata at the pile tip of single-row double-pile and single-row three-pile foundation of the underlying cav? ity bridge is analyzed by the theoretical method and numerical simulation. The results show that：（1）when the pile spacing L is small，the local overlap of punching shear occurs；（2）when the pile spacing L is twice the pile diam? eter，the total bearing capacity of single row double piles and three piles of the bridge is 75 % and 67 % of the total bearing capacity without considering the superposition effect，respectively. With the gradual increase of pile spacing L，the total bearing capacity of the pile end rock of double piles and three piles increases gradually. When the pile spacing L reaches five times the pile diameter，the bearing capacity reaches more than 99 % of the total bearing ca? pacity without considering the superposition effect.