Abstract: Borehole instability tends to cause severe downhole troubles and increases the drilling costs greatly. Accurate geomechanical model can provide the technical support for well drilling. In this paper, the logging data, geomechanical testing results, formation fracturing pressure testing results and drilling log of the deep exploration well along the southern margin of the Junggar Basin were adopted to plot the rock mechanical property and pressure profile of its neighboring well and establish the one-dimensional geomechanical model. Then, the three-dimensional geomechanical model of the whole well block was established by virtue of the multi-well geomechanical profile. Based on the three-dimensional geomechanical model, the borehole instability problems of ultradeep wells caused by abnormal formation pressure, hole wall collapse and other downhole troubles can be reduced. When the three-dimensional geomechanical model is used for practical drilling, non-production time caused by downhole troubles is 25.3 % less compared with the neighboring well. This method provides the convenient means for the drilling fluid density optimization and risk evaluation of deep exploration wells in Gaoquan structure along the southern margin of the Junggar Basin and the safety evaluation of high temperature and high pressure wells, as well as the guidance for diminishing drilling risks and improving drilling situations.