Regulating line with the optimum fuel economy performance is investigated based on the universal characteristic map of the engine equipped on the snowmobile. The engine is supposed to run in a range near the optimum fuel economy performance regulating line with CVT speed regulating control. The dynamic model of the snowmobile is proposed, and simulation with Simulink is investigated. Though acceptable deviation occurs when compared with experimental results, reliability is validated for the model. With further amendments of the model, such as a further consideration of the slip state of the CVT when launching the snowmobile, the model can be applied to the practical engineering as an effective design tool.