A mechanical model of bottom hole assembly (BHA) with eccentric bits is established and the solution of this model was given by means of numerical method.

It still is a difficult subject for most drilling engineers to predict and control well path by applying the mechanical analysis of bottom hole assembly and the rock-bit interaction model.

The force and deformation of bottom hole assembly (BHA)are calculated by the gap-element method, in consideration for the bending effect and contact state of BHA.