The construction of small diameter core drilling in the tunnel of Gansu Jinchuan Company has poor geological conditions and low construction efficiency. The newly launched deep ore exploration drilling project in the second mining area generally has a meterage per rig-month of no more than 150m， and there are many drilling accidents and scrapped boreholes. The main reason is that there are many accidents in the hole caused by the high pressure of the surrounding rock and the instability of the hole wall caused by water gushing during drilling in the altered formation. The effect of mud wall protection is not ideal， and drilling tool breakage and new hole phenomena often occur during hole cleaning. When drilling with a depth of more than 300m， it is common to encounter stuck or buried drilling accidents. Based on the construction experience of the mining area， this article proposes economic and practical treatment methods for drilling in complex formations with high stress and strong corrosion： drilling with casing， mud mixing， high-pressure grouting， and handling of stuck drilling accidents. Among them， high-pressure grouting is rarely used in the construction of complex formations in small diameter core drilling. In suitable formations， grouting can not only reduce the number of casing used， but also improve the stability of the hole wall. It is a practical and worth promoting technical method.