A power system of a series hybrid vehicle, comprising: a fuel source; a control system; six or eight auxiliary power units, wherein each of the auxiliary power units, under control of the control system, independently receives fuel from the fuel source, and converts chemical energy in the fuel into electrical energy and outputs the electrical energy to a common current bus, wherein each of the auxiliary power units comprises: an engine, which, under control of the control system, receives fuel from the fuel source and converts the chemical energy in the fuel into mechanical energy; and a generator, which, under control of the control system, receives mechanical energy from the engine of a corresponding auxiliary power unit and converts the mechanical energy into AC or DC electrical energy; a power battery electrically connected to the common current bus to, under control of the control system, receive electrical energy from the common current bus to perform charging, or perform discharging through the common current bus; and a traction motor electrically connected to the common current bus to, under control of the control system, receive electrical energy from the common current bus, and convert it into mechanical energy and transmit the mechanical energy to a power train of the vehicle so as to drive the vehicle to run; wherein each of the auxiliary power units further comprises: an electrically controllable clutch, which is arranged in a transmission path of mechanical energy from the engine to the generator, so that the transmission path of mechanical energy from the engine to the generator is connected or disconnected under control of the control system; wherein during travel of the vehicle, the power requirement of the vehicle is met by selectively activating or deactivating one or more of the auxiliary power units; and wherein the activating and deactivating is obtained by connecting or disconnecting the electrically controllable clutch of the one or more of the auxiliary power units, while arranging the engine of each started auxiliary power unit to work in an optimal working condition power section around an optimal working condition point of the engine, and wherein the optimal working condition power section is from +10% to -20% of the optimal working condition point of the engine of each auxiliary power unit. a fuel source; a control system; an engine, which, under control of the control system, receives fuel from the fuel source and converts the chemical energy in the fuel into mechanical energy; and a generator, which, under control of the control system, receives mechanical energy from the engine of a corresponding auxiliary power unit and converts the mechanical energy into AC or DC electrical energy; a power battery electrically connected to the common current bus to, under control of the control system, receive electrical energy from the common current bus to perform charging, or perform discharging through the common current bus; and a traction motor electrically connected to the common current bus to, under control of the control system, receive electrical energy from the common current bus, and convert it into mechanical energy and transmit the mechanical energy to a power train of the vehicle so as to drive the vehicle to run; wherein each of the auxiliary power units further comprises: an electrically controllable clutch, which is arranged in a transmission path of mechanical energy from the engine to the generator, so that the transmission path of mechanical energy from the engine to the generator is connected or disconnected under control of the control system; wherein during travel of the vehicle, the power requirement of the vehicle is met by selectively activating or deactivating one or more of the auxiliary power units; and wherein the activating and deactivating is obtained by connecting or disconnecting the electrically controllable clutch of the one or more of the auxiliary power units, while arranging the engine of each started auxiliary power unit to work in an optimal working condition power section around an optimal working condition point of the engine, and wherein the optimal working condition power section is from +10% to -20% of the optimal working condition point of the engine of each auxiliary power unit. an electrically controllable clutch, which is arranged in a transmission path of mechanical energy from the engine to the generator, so that the transmission path of mechanical energy from the engine to the generator is connected or disconnected under control of the control system; wherein during travel of the vehicle, the power requirement of the vehicle is met by selectively activating or deactivating one or more of the auxiliary power units; and wherein the activating and deactivating is obtained by connecting or disconnecting the electrically controllable clutch of the one or more of the auxiliary power units, while arranging the engine of each started auxiliary power unit to work in an optimal working condition power section around an optimal working condition point of the engine, and wherein the optimal working condition power section is from +10% to -20% of the optimal working condition point of the engine of each auxiliary power unit.