1. A speech recognition system, used for receiving a speech signal and output an output language word with respect to the speech signal, wherein the speech recognition system has a first threshold, a second threshold, and a third threshold, the speech recognition system comprising: a first speech recognition device, used to receive the speech signal and generate a first candidate language word and a first confidence measurement of the first candidate language word, according to the speech signal; a second speech recognition device, used to receive the speech signal and generate a second candidate language word and a second confidence measurement of the second candidate language word, according to the speech signal; and a confidence measurement judging unit, used to judge and output the output language word, according to the first confidence measurement and the second confidence measurement; wherein when the first confidence measurement is less than the first threshold and the second confidence measurement is less than the second threshold, the first candidate language word is taken as the output language word, when the first confidence measurement is greater than the first threshold and the second confidence measurement is less than the third threshold, the first candidate language word is set to be the output language word, when the first confidence measurement is less than the first threshold and the second confidence measurement is greater than the second threshold, then the second candidate language word is set to be the output language word, and when the second confidence measurement is greater than the third threshold, the second candidate language word is set to be the output language word.