1. An information extraction method, for extracting dynamic information, the information extraction method comprising: building a plurality of information extractors for connecting with a plurality of information sources, wherein each of the information sources provides the dynamic information; setting a weight value for each of the information extractors; recording a first reference value of the dynamic information extracted by each of the information extractors from each of the corresponding information sources at a first time point, and determining a first reliable value corresponding to the dynamic information according to the first reference values; using each of the information extractors to extract a second reference value of the dynamic information from each of the corresponding information sources at a second time point; determining a second reliable value corresponding to the dynamic information at the second time point according to the weight values and the second reference values; and verifying whether the information extractors are abnormal, and when one of the information extractors is verified as an abnormal information extractor, removing the verified abnormal information extractor.