The invention relates to a parallel connection split type fuel oil system and an oil supply method of the parallel connection split type fuel oil system. The fuel oil system comprises a main oil tank,an auxiliary oil tank and a six-way reversing valve. The bottom of the main oil tank and the bottom of the auxiliary oil tank are connected through a communicating pipe. The main oil tank is connected with an oil inlet A and an oil outlet B of the six-way reversing valve through a first oil conveying pipe and a first oil return pipe correspondingly. The auxiliary oil tank is connected with an oilinlet C and an oil outlet D of the six-way reversing valve through a second oil conveying pipe and a second oil return pipe correspondingly. An oil outlet E and an oil inlet F of the six-way reversing valve are used for being connected with an engine through pipelines. The parallel connection split type fuel oil system has the advantages of being simple in structure, convenient to use, safe and reliable, and can effectively increase the driving range of a vehicle. The oil supply method has the advantages of being simple in process, reasonable in logic and high in reliability.