The invention relates to a wind generator gear lubricating oil on-site regeneration treatment system and method. The system includes a vacuum dehydration system, a regeneration system, a filtration system, a heating system, an additive automatic replenishing system, an oil quality on-line monitoring system, a cleaning and filling system, a magnetic filtration system, a circulating oil pump and an oil suction valve. Waste oil is sucked into a vacuum tank of the vacuum dehydration system, the circulating oil pump pumps the oil out from the bottom of the vacuum tank, after passing through the heating system, the magnetic filtration system, the regeneration system and the filtration system, the treated oil is returned to the vacuum tank from the vacuum tank top. The on-line monitoring system monitors the oil product parameters in real time during regeneration, after removal of degradation products from the oil product, an additive is added according to the index parameters of recovered oil, the cleaning and filling system performs repeated flushing on a waste oil drum and loads the qualified oil obtained by regeneration treatment into the cleaned oil drum. The replaced waste gear oil is subjected to regeneration treatment and on-line quality monitoring on site, thus ensuring that the oil subjected to regeneration treatment meets the standard requirements.