In recent years, the number of geological drilling hole accidents has declined. However, due to the changes in technical and economic conditions, the geological drilling applications and scope have expanded with the increasing of drilling depth and the complicated downhole situation. Once downhole accident occurs, the construction becomes even harder.〖JP〗 It is necessary to sort out the complex cases and the types of accident in drilling hole as soon as possible and establish the technical rules for the downhole accidents prevention and treatment to promote the development and standardization management of the downhole accident prevention and treatment. There are many kinds of complicated case in the geological drilling hole, such as drilling leakage/water gushing, borehole bending, borehole temperature anomaly, borehole diameter reduction/expansion, hole collapse/blockage, hole sedimentation, foreign matter in hole and other abnormal situations in hole. The types of accidents in geological drilling holes mainly include drilling tool accidents, stuck drilling pipe accidents, burial drilling accidents, bit burnt accidents, casing accidents, logging accidents, coring accidents and other accidents. There are great technological differences between geological drilling and oil and gas drilling, the complex cases in holes and accident types are also different, for geological drilling, the types of accident in oil and gas drilling can not be applied mechanically, but the advanced technology and management ideas of downhole accidents prevention and treatment in oil and gas drilling industry should be learned.