Disclosed are a passive optical network business flow sensing method and system and a storage medium. The method comprises: by a master control layer, extracting business flow characteristic parameters according to an obtained training sample set, performing pre-processing on the business flow characteristic parameters, and determining a business flow characteristic set; performing Bayes training according to the characteristic set, updating parameter information of a Bayes classifier, and sending the parameter information to an agent layer; by the agent layer, periodically collecting business flow characteristic parameters and updating the training sample set, and establishing a corresponding Bayes classifier according to the parameter information; determining, according to the updated training sample set, the updated business flow characteristic set, and determining, according to the updated characteristic set and the Bayes classifier, a classification identification result; and performing business optimization adjustment according to the classification identification result.