Abstract: The voting logic algorithm concerns whether the faulttolerant controller can exactly diagnose the error information of channel. This paper proposes an algorithm of voting logic by word. By comparing the output word of each channel of the system, the algorithm can deal with the problem that the voting algorithm by bit can only output error signals but not output result. In the application example of triplefaulttolerant controller based on voting logic by word, both the automatic conversion links and selfchecking monitoring circuits are added to the controller such that the reliability of system can be improved. The application result shows that the voting logic by word is of higher reliability, which can improve the faulttolerance performance of the system.