The invention provides a method and system for on-line word selection input. The method and system for on-line word selection input are suitable for an electronic device. The method comprises the steps of first logging in to a far-end word selection database through a network, identifying an application program focused by a cursor of the electronic device so as to be connected with a subdata base corresponding to the application program in the word selection database, receiving characters input by users so as to search a plurality of words relevant with the characters in the subdata base and the sequence of the words, sequentially displaying the words, and finally receiving selection operation on the words by the users so as to input the selected words.