1. A sorting method of data documents, adapted to an electronic device, comprising: retrieving, by the electronic device, at least one first keyword from a content of a first data document; retrieving, by the electronic device, a keyword ranking corresponding to the at least one first keyword by a search engine on the Internet; searching, by the electronic device, a keyword category corresponding to the at least one first keyword on the Internet; and inputting, by the electronic device, the at least one first keyword, the keyword ranking and the keyword category of each of the at least one first keyword into a sort algorithm thereby outputting, by the electronic device, a predicting ranking of the first data document to sort the first data document, wherein the sort algorithm is generated based on contents of a plurality of second data documents and a current ranking of each of the plurality of second data documents, and generating the sort algorithm comprises: retrieving a plurality of second keywords from the contents of the plurality of second data documents; retrieving keyword rankings corresponding to the plurality of second keywords by the search engine; searching keyword categories corresponding to the plurality of second keywords; and generating the sort algorithm by setting the keyword ranking and the keyword category of each of the plurality of second keywords as an input of the sort algorithm and setting a current ranking of each of the plurality of second data documents as an output of the sort algorithm.