The present invention discloses a database search system comprising: a composite database search engine, comprising at least two database search tools wherein at least one is database search agent; a database search agent establishing and training module to automatically generate a database search agent according to analysis of a data file and to automatically modify content of said database search agent according to content of another database search agent; each database search agent comprising a series of search indices and their weight values; and user interface to allow user to actuate any of said database search tools to input evaluation of searched data files to be desired or not; wherein said database search agent establishing and training module modifies database search agent according to content of searched data files determined to be desired by user.