The invention discloses a mode selection control method and device of an electromechanical coupling gearbox. The mode selection control method comprises the following steps that it is determined thatthe current work mod of a vehicle is an idling mode or driving mode according to a current vehicle driver operation signal; if the current work mode is the idling mode, a neutral gear power generatingmode or neutral gear engine stop mode is selected according to the current battery remaining electric quantity value; and if the current work mode is the driving mode, the current needed output poweris determined according to the current accelerator pedal opening degree value and vehicle speed, a pure electric mode or hybrid mode or range extending mode is selected according to the comparison result of the current remaining electric quantity value, the vehicle speed and battery peak value discharge power and the current needed output power, and the pure electric mode, the hybrid mode and therange extending mode are switched. The device is used for achieving the method. According to the mode selection control method and device, two power sources, namely, an engine and a battery can coordinate and cooperate well.