Abstract: To guide development and application of automatic vertical drilling tools and provide theoretical basis for optimum design of bottom hole assembly of automatic vertical drilling system, the one dimensional (1-D) mechanics analysis model of bottom hole assembly (BHA) equipped with automatic vertical drilling tools is developed by using the beam-column method, the general dynamics equation of BHA is established, boundary conditions at bits and the upper tangent are determined, and the formula is deduced for calculating lateral forces and deflection angles of bits, based on the research of structural features and work principle of automatic vertical drilling system.By applying the model, the bending moment of stabilizer pivots and the bending deflection of the beam column can be exactly calculated.Meanwhile, the law of lateral forces and deflection angles of bits changing with drilling parameters can also be used to analyze the effect of the drilling parameters on deflecting forces of automatic vertical drilling tools, providing theoretic basis for directing field application of automatic vertical tools.