In view of the engineering problem caused by the damage of the gravity quay protection unit under the action of the ship jet，the Dutch method and the German method recommended by PIANC，as well as the algorithm recommended by The Rock Manual，are analyzed and compared.It is concluded that the Dutch method is more suitable for the design of block stone bottom protection，and the German method has good applicability in the problem of homogeneous soil or graded soil erosion；gravity wharves can appropriately increase the calculated value of the bottom protection erosion velocity.Based on the research results，taking a port project in Africa as an example，the Dutch method is used to design the gravity quay protection unit.