Because of the strong weathered rock fracture joints developing and uneven degree of rock weathering as well as uneven rock hardness, the conventional composite bit are replaced by impregnated diamond bit, which makes the grinding mode change to cutting mode in the drilling process to improve drilling efficiency; in order to improve the core recovery and protect the strong weathered cores in the coring tool and avoid the core segments from grinding each other, the single pipe drilling tool is replaced by single-action double pipe drilling tool. Relatively high quality mud is used to protect wall and prevent drill pipe sticking in drilling and tripping.