Circulation loss has been a technical challenge in drilling work. It is always a key point to find effective and quick solutions to circulation loss in drilling in the Ruoergai uranium mining area under different working conditions. Large circulation loss was encountered in drilling the ZK4-5 borehole with gravity falls of the drilling string for several times, and cement plugging was done with little effect. Under the condition of the limited borehole diameter, the slim corrugated tubing was adopted to deal with the large circulation loss formation successfully, providing reliable technical support for sealing large circulation loss formation.