The invention belongs to the field of big data processing technology and discloses a thematic knowledge automatic mining system and method. The system comprises an Internet-of-Things interface module,a semantic query module, a data mining module and a map aggregation and visualization module. The method comprises the steps that first, data collection and database establishment are performed, wherein data acquired based on a web ubiquitous network, data of monitoring sensors and all types of thematic data are collected, sorted out and stored into a thematic database; next, thematic knowledge mining is performed, wherein thematic knowledge is formed through ontology construction, semantic query and depth information mining, and a file is transmitted into an FTP file server; the thematic knowledge acquired from the FTP file server and a geographic base map are subjected to geographic correlation, and cartographic data is formed; surface format design, thematic chart design and surface finishing are performed; and finally a thematic map is output. According to the thematic knowledge automatic mining system and method, by aid of a machine learning algorithm under big data, huge territorial resource information can be processed and analyzed through an efficient and accurate method.