The disadvantage which the algorithm EC for mining frequent item over data streams was analyzed,such as the inaccurate of the frequent item mined in a recent period of time over the data stream.Put forward a data structure the frequent item sample in the form of 4 member group.Then,presented an algorithm SWFPM which based on sliding window for mining frequent item over data streams.The SWFPM algorithm can accurately mine the frequent item over the sli...