In recent years, with the increasing complexity of the exploration and development geological environment, the number of complex wells increases, and subsequently, the borehole stability becomes more and more an issue. This paper proposes a method to predict the borehole stability during drilling of directional wells based on a geological statistical analysis. Firstly, the seismic and logging data of drilled wells are analyzed, and then through the geostatistical collocated co-Kriging simulation combined with the sequential Gaussian simulation, the 3D data body of rock mechanics parameters for the whole block are predicted. According to the trajectory to be drilled, the parameters of rock mechanics for the wellbore trajectory are extracted and by using the models for collapse, fracture and pore pressure of the directional well, the prediction model for the corresponding stratified rock mechanics is built. The accuracy of the prediction can be evaluated in comparison with the logging data and by adjusting the parameters of the model, the model can be updated and refined to improve the prediction accuracy.