The software, implementing the mathematical model of a horse rider with four links, is presented in the article. The rider is on the horse, which is a mobile base. Unlike to the previously compiled models, this research considers the start-up operations and the accelerated motion of the horse. The local systems of coordinates are used in the software for describing dynamics of the rider on the mobile horse. These systems are more suitable for specifying the angles between the links, which corresponds to the rider's biomechanics, whose musculoskeletal system changes these angles, applying internal efforts. The algorithm of compiling the system of equations of motion using the Lagrange equations of the second kind is implemented in the software. The programmed motion control is applied to the model. The accelerated motion of the mobile base in the form of horse as well as the angles between the rider's links are specified by analytical differentiable functions, synthesizing the mechanical system motion resembling that of a real horse rider. Using the created software, the inverse dynamics problem has been solved. The control torques, changing the angles between the links, and the reactions of mobile base are found. The presented software, the mathematical model of the system, and the results of the research can be used for formulating recommendations for designing programming exercise machines with various working modes, which allow for rider training regardless of environment and weather conditions, horse fatigue, stable remoteness, and other aspects. It will allow horsemen to practice complex skills without fear of possible injury.