Flexible fuel engine control system and control method

The invention discloses a system for controlling flexible fuels, which comprises an oil injector, an oil rail and a main oil supply system, and an auxiliary oil supply system as well as a cleaning system, wherein the auxiliary oil supply system is used for cold starting, and the cleaning system comprises an oil return pipe for connecting the oil rail and a main oil tank, and an electromagnetic valve controlled by an engine controller. When the engine controller judges that gasoline is needed to assist the cold starting, the electromagnetic valve is controlled to turn on, an auxiliary pipe pump is controlled to operate, and alcohol fuels in the oil rail is cleaned to the main oil tank by the gasoline in an auxiliary oil tank. After an oil path is cleaned completely, the engine controller controls the electromagnetic valve to turn off, the engine is started to enter the cold starting mode, and after the cold starting is ended, the engine is automatically switched into the alcohol fuel mode of the main oil tank