The invention relates to a public opinion monitoring system based on a data mining technology. The public opinion monitoring system comprises a data obtaining unit, a fragmentation unit, a calculation unit, a cache unit, an output unit, a modelling unit and a prediction unit, wherein the data obtaining unit is used for crawling public opinion initial data of the internet through a network crawler program; the fragmentation unit is used for performing input fragmentation of the public opinion initial data of the internet; the calculation unit is used for combining repetitive key values in an intermediate file so as to reduce the redundancy of mapped output files; the cache unit is used for opening up an annular memory buffer area in a memory; the annular memory buffer area is used for outputting the mapped output files; the output unit is used for storing all the mapped output files in a distributed file storage system; the modelling unit is used for establishing a network public opinion prediction model; and the prediction unit is used for reading the mapped output files from the distributed file storage system, and performing public opinion through the network public opinion prediction model.