The invention discloses a power system of an extended-range type electric vehicle adopting a combination of a double clutch and planetary gears. The power system comprises an internal combustion engine, a planetary gear system, a first motor, a second motor and the double clutch. The planetary gear system comprises a planetary carrier, the planetary gears, a gear ring and a sun wheel. An output shaft of the internal combustion engine is connected with the planetary carrier. A rotor of the first motor is connected with the gear ring. The sun wheel is connected with one end of a transmission shaft, and the other end of the transmission shaft is connected with an input disc of the double clutch. A rotor of the second motor is connected with the input disc of the double clutch. The output end of a first clutch part of the double clutch is provided with a first driving gear, and the output end of a second clutch part of the double clutch is provided with a second driving gear. The first driving gear is meshed with a first driven gear. The second driving gear is meshed with a second driven gear. The first driven gear and the second driven gear are arranged on a power output shaft.