The invention discloses a method for extracting a datum from one or more data resource. Each data resource comprises multiple data. Each datum comprises one or more data item in a key-value pair form. A data extraction method comprises the following steps: confirming the data type corresponding to each key for each data resource and generating a data type table; analyzing one datum and extracting one or more data item contained in the datum; for each data item, extracting a key-value pair forming the data item; confirming the data type corresponding to the extracted key from the data type table according to the data resource of the datum; utilizing a data verification method corresponding to the data type to verify the value in the extracted key-value pair, wherein if the value passes the verification, then extracting is successful; and recording the value in the extracted key-value pair. The invention also discloses a corresponding data extraction device and a corresponding data extraction system.