The hole-wall stability is one of the focuses of deep-hole geological core drilling. The accurate prediction of formation pore pressure, in-situ stress state, formation collapses pressure and fracture pressure before drilling are vital to conduct quality, safe, efficient and low-cost drilling. These are the design basis of the hole-wall structure, casing program and strength, density and rheological properties of drilling fluids. Based on the hole-wall stability, discussion is made on the existing problems of hole-wall structure, casing program, drilling tool assembly, drilling equipment in deep-hole geological core drilling and suggestions are put forward for the improvement.