Abstract: This article introduced a two-out-of-three Safety-critical Computer System which was used in on-board equipment of railway transport. The System consisted of three same subsystems, was developed with fault-tolerant technology and the VxWorks real-time operating system. The characteristic of three series redundant fault-tolerant system is the shielding effect to the single line fault, reflects the continuity in the control process and seamless handover after breakdown.