The disclosure relates to a self-adaptive oil spraying control system and method for a biodiesel engine. The control system includes an exhaust pipe, a gas sensor, a control module and an oil sprayer, wherein the exhaust pipe is connected to the oil sprayer, the gas sensor is mounted in the exhaust pipe, and the gas sensor and the oil sprayer are connected to the control module respectively. According to the control method, a main spray advance angle of the engine is subjected to closed-loop control directly through comparison between an idling steady state NOx emission signal and an idling steady state NOx emission value of pure diesel when the engine uses the biodiesel, so that emission of NOx in the exhaust is reduced. Compared with the prior art, the disclosure has the advantages of no need of detecting a biodiesel ratio, high efficiency, good effect and the like.