The invention relates to a device for regulating the thermoelectric generation power matched load in real time by changing heat transfer areas and belongs to the technical field of engines. The device comprises a tail gas inlet, a thermoelectric generation piece unit, a cooling liquid circulating body, a tail gas reutilization electromagnetic valve, a tail gas reutilization guide pipe, a tail gas outlet, a heat transfer piece mechanism, a tail gas outlet temperature sensor, a tail gas inlet temperature sensor and an electronic control unit. The lengths of heat transfer pieces in the heat transfer piece mechanism can be adjusted; and by adjusting the lengths of the heat transfer pieces and changing the heating areas of the heat transfer pieces, the heating temperature of the heat transfer pieces is changed, and accordingly power generated by a power generator is changed and made to be matched with the electricity load power. According to the device for regulating the thermoelectric generation power matched load in real time by changing the heat transfer areas, waste heat energy of an engine is fully utilized, and the utilization rate of fuel is increased; and the heat exchange areas of the heat transfer pieces are adjusted in real time according to the electricity load condition, the power of the power generator on the engine can be reduced, the loss of accessories of the engine is reduced, and accordingly the efficiency of the engine is further improved.