Time synchronization is one of the key points in distributed of a real-time simulation system. At first, a distributed simulation system is introduced. Secondly, time synchronization method under 1PPS signal is put forth. Thirdly, the relevant technology of time synchronization are studied, including system structure, SNTP, 1PPS signal and control logic. Vxworks watch dog timer mode and timecard counter mode under this method are also analyzed in detail and the precision is presented. Fourthly, Arena software is chosen to model and simulate the time synchronization procedure. At last, the whole simulation model is constructed and the experiment results are given out to prove the efficiency of the synchronization method.