The invention discloses a mounting method of a breakwater barrel type component. Four pulling rings are reserved on the root of a barrel type component and are symmetrically arranged on the front part and the rear part of the barrel type component; two mooring ropes are connected between the a semi-submersible barge front part and a pulling ring at the rear part of the barrel type component; two mooring ropes are connected between a semi-submersible barge rear part and the rear part of the barrel type component; cross mooring ropes are connected between the pulling rings at the front part of the barrel type component and a main pulling ship; after the barrel type component floats in a right place via air, drainage and exhaust are subjected to centralized management by drainage pumps and an exhaust valve; each pump is adjusted to be switched on and off at any time; the barrel type component continues to drain synchronously after the balance of the barrel type component is ensured; the barrel type component sinks via negative pressure until the sinking depth of the barrel in the mud is 2.0-3.0m; all the drainage pumps are switched off; and the sinking operation is completed. According to the mounting method of the breakwater barrel type component, the mooring ropes are used for pulling the barrel type component; due to coordination of large tonnage of the barrel type component, the barrel type component can be leveled in the air floating and mounting process; the balance can be controlled in time; the carrying and mounting efficiency is improved; the construction can also be carried out under the severe weather condition.