Abstract: This paper presents a duplex redundancy fault-tolerant system of 8031 single-chip microcomputsr (SCM )，in which many kinds of techniques,including pulse synchronization, error detection with bus sampling comparison，and checkpoint recovery，etc. are applied.
The system is of the functions of fault rollback recovery,diagnosis for isolation and degraded running. Therefore，its reliability has greatly been improved.

Key words: Single-chip microcomputers fault-tolerant compu