In order to solve the problem of hard rock layer in dredging,which cannot be or is not suitable to be treated by blasting,this paper takes Angola Luanda SONILS quay wall project as an example,and stndies the application of mechanical rock breaking method in dredging.Based on the analysis of the practical conditions in the field,this paper puts forward the best treatment scheme for rock breaking by using rock hammer or piling barge,and selects the appropriate construction parameters such as hammer shape,hammer weight,free fall height and arrangement of rock impact points through theoretical analysis,and makes experiments and improvements.In the process of implementation,attention should be paid to the wear and reinforcement of the steel wire and hammer tip as well as the sealing of the pile tip.The results show that after mechanical breaking,the hard rock layer can be easily cleaned by grab dredger,has good economic benefits,and may serve as reference for the similar project.