A downhole tractor is a quick and efficient means of transporting logging devices and its obstacle performance directly influences the quality of the tractor's work and is a critical element in studies of the tractor over-obstacle process. The construction of a faithful tractor over-obstacle model comprises (1) studies of the over-obstacle statics of the downhole tractor, including the relationship between the driving force of the motor, tractor resistance, and the height of the obstacle, along with the derivation of the static balance equation of the tractor over-obstacle process; (2) a dynamic analysis of the downhole tractor over-obstacle process, including compilation of the system of dynamic D'Alembert initial force equations and the system of D'Alembert inertial moment equations, and a more detailed description of the downhole tractor over-obstacle process, along with a more accurate calculation of the driving force required by the downhole tractor. It was found that matches downhole tractor prototype test data matches the data calculated by the analytic method. The use of the dynamic equations can increase the over-obstacle success rate of the downhole tractor in a horizontal well and solves the technical problems involved in overcoming obstacles.