The invention relates to a method and system for detecting anomalous bundles of banknote products, and a sorting machine. The detection method comprises the following steps of, when a banknote productis delivered to the banknote outlet of the sorting machine, obtaining product image information of the banknote product, wherein the product image information includes bundle status information at apreset area of the banknote product, the bundle status information includes the current reflectance and a bundle inclination value, the current reflectivity is the reflectivity at the preset area, andthe bundle inclination value is the angle between the bundle and the vertical central axis of the banknote product; determining whether the current reflectance or the bundle inclination value is within a corresponding preset parameter range; if at least one of the current reflectance or the bundle inclination value is not within the corresponding preset parameter range, generating an abnormalityalarm message, and controlling the sorting machine to stop the sorting operation. The invention can effectively check the abnormality during the bundling of bundles, and ensure the accuracy of the bundling.