The invention discloses a drill bit adjustment predicting method for geological guidance. The method comprises the following steps: geological guide models are built by using history adjoining well and/or guide hole well logging data; well hole stratum relative dip angles, stratum direction angles and boundary distance indicating polarization values are calculated by using direction gammas while drilling and electromagnetic wave resistivity log curves obtained in real time to correct the geological guide models and to build stratum initial models while drilling; based on response results of the stratum initial models while drilling, the models are corrected; according to preset geological model inversion databases, stratum real parameters are obtained through a quick database searching method; and according to the stratum real parameters, the change of layer interfaces in the well shaft directions of horizontal wells to be drilled is predicted, and adjusted safety distances of drill bits in target layers are calculated. The method can predict the stratum directions and the distances from the drill bits to the layer boundaries through conventional logging data while drilling, so that the logging data utilization efficiency is improved, and the geological guidance operation of engineers is directed.