The invention provides a method for synchronizing three-redundancy computers. The method is characterized in that a voting module is used for providing three paths of synchronous pulse signals for a redundancy computer system; a CPU (central processing unit) of a redundancy computer is used for detecting faults of the three paths of synchronous pulse signals, and a uniform synchronous pulse signal is determined by the same switching strategy, so that the continuous high-precision synchronous clock signal still can be provided for the redundancy computers when a clock system has one or two-fault state, thereby improving the reliability of the redundancy computer system; by adopting the uniform synchronous pulse signal, and performing state interaction among the three redundancy computers, the synchronism of software time references of the redundancy computers is guaranteed, the synchronous pulse signals are used as soft-terminal triggering signals during real-time execution of the software, and the synchronizing of the working process of the redundancy computers is guaranteed. The synchronizing method has the advantages that the time error of the redundancy computation is less than 10mu s, the realizing of the synchronizing method is simple, and the method is favorable for the realizing of engineering.