The invention relates to a double-source power system and a control method thereof. The system comprises an internal combustion engine, a low-temperature working medium storage tank, a heat exchanger, a turbine and a motor, wherein the internal combustion engine is internally provided with an exhaust unit and a cooling unit; a low-temperature working medium is stored in the low-temperature working medium storage tank; the heat exchanger transmits heat to the exhausted gas of the exhaust unit, the cooling water of the cooling unit and the low-temperature working medium to lower the temperature of the exhausted gas and the cooling water; meanwhile, the low-temperature working medium is subjected to heating vaporization so as to be expanded to form high pressure gas; the turbine is connected with the heat exchanger and the internal combustion engine; a gas inlet receives the high pressure gas flowing out from the heat exchanger; a gas outlet is connected with the internal combustion engine; the heat energy of the high pressure gas is transformed into mechanical energy; the motor is connected with the turbine, and is driven by the turbine so as to generate power or do work outwardly; the mechanical energy is stored as electric energy, or the mechanical energy is used for doing work outwardly. Compared with the prior art, the system and the method have the advantages that the energy utilization rate of the power system is further improved, while the satisfaction on the power change demands under the complicated conditions of traffic transportation is guaranteed.