At present，the most widely used petrol-type mountainous orchard transporter adopts the low-cost carburetor-type engine with low combustion efficiency and poor emissions.Pure electric transporter is difficult to promote in mountainous orchards due to the limited capacity and inferior cruising mileage.A range-extender system based on the existing electric mountainous orchard wheel transporter was designed with the Advisor simulation instrument.A range-extender system with a total capacity of 120 A·h and voltage of 60 V lead-acid battery as the major power and 5 kW range extender device as assistant power was proposed to satisfy the design requirements of the maximum load of 240 kg，the maximum climbing slope of 15° and the maximum speed of 9 km/h.In the extended mode，the running distance of the transporter is 52.2 km when the load is 240 kg,217.5% longer than that of the pure electricity mode.The mileage is improved significantly．