The invention provides an intelligent discrimination flushing system of a closestool, which comprises a sensor module, a flushing module, a time statistics module and an intelligent judgment module. The invention also provides a flushing method of the system, which comprises the steps of: when a user sits on the closestool and then leaves the closestool, judging whether the sitting time is longer than M seconds or not, if the sitting time is shorter than or equal to M seconds, judging the use to be abnormal, and enabling the flushing method not to respond; if the sitting time is longer than M seconds, judging the use to be normal, and flushing more water within N seconds after the user leaves the closestool; when the user leaves the closestool and then sits on the closestool again, judging whether the leaving time is longer than P seconds or not; if the leaving time is longer than or equal to P seconds, judging that the user leaves the closestool normally, repeating the previous step; if the leaving time is shorter than P seconds, judging that the user leaves the closestool abnormally, and further judging whether another sitting time is longer than Q seconds or not; if the another sitting time is shorter than or equal to Q seconds, judging that the user sits on the closestool abnormally, and enabling the flushing method not to respond; and if the another sitting time is longer than Q seconds, judging that the user sits on the closestool normally, and flushing more water within N seconds after the user leaves the closestool.