In order to reduce the pollution caused by a normal car at low speeds especially in the urban area, a parallel hybrid car with a metal belt-planetary gear continuously variable transmission (CVT) is researched. Compared to a normal electric car with gear transmission system, it has such advantages as larger starting torque, lower power, lighter weight and so on. The simulation equations on the dynamic characteristic of electric car with a DC motor are established using bond graph theory. The control rules of the armature current of motor and ratio of continuously variable transmission are obtained. The design method of a parallel hybrid car is established.