A consistent checkpointing algorithm with short freezing time (SFT)is presented in this paper. It supports fault-tolerance in distributed systems. The algorithm has shorter freezing time, lower overhead, and simplicity of recovery. To make checkpoint time shorter, a special control message (Munblock) is used to ensure that a process can respond the checkpoint event quickly at any given time. Moreover,main memory algorithm is used to improve the concurrency of checkpointing. By using SFT, the freezing time resulted by checkpointing is less than 0.03s. Furthermore,the control message number of SFT is only O(n).