The paper introduces the experimental application of BH-114 casing drilling for hole ZK9501 in the complex formation of Makeng iron ore of Fujian. In the experiment, the WOB and torque were transferred by φ114mm casing instead of wire-line drill rod to drive the casing coring tools and based on the wire-line coring catching principles, core drilling was carried out and the main and auxiliary bits were replaced without drill string lifting until drilling across the complex formation to the determined depth. The wall instability caused by drill string lifting and downhole trouble were avoided to reduce the labor intensity, improve the construction environment and promote safe production.