The invention provides an oxygen-rich combustion air leak monitoring method and system. The method comprises the following steps: acquiring carbon dioxide concentration measured values of multiple monitoring points in a boiler equipment system or flue gas flow values of the multiple monitoring points, wherein the multiple monitoring points are disposed at the inlets and the outlets of multiple different devices of the boiler equipment system; and according to the multiple carbon dioxide concentration measured values or the multiple flue gas flow values, calculating air leak rates of the multiple different devices in the boiler equipment system and/or a total air leak rate of the boiler equipment system. According to the invention, air leak can be monitored, and air leak points are timely controlled according to the air leak rates of the different devices and/or the total air leak rate of the boiler equipment system which are calculated in real time, so that high-concentration enrichment of carbon dioxide is realized.