The invention discloses a MapReduce system and a method for processing data streams, belonging to the technical field of computers. The MapReduce system comprises M Map modules and R Reduce modules, wherein each Map module comprises a raw data stream data acquisition unit, an intermediate result data acquisition unit, an intermediate result data segment acquisition unit and an intermediate result data segment processing unit; and each Reduce module comprises a Reduce processing unit. The MapReduce system and the method provided by the invention have the following beneficial effects: in the process of parallel processing of the data streams, outputs of the Map modules are combined to form a segment and then Reduce processing is carried out on the segment, so that the MapReduce system can support data stream processing, thus breaking through the limitation that the conventional MapReduce system can not process the data streams.