In order to solve the time synchronization problem in tandem hot strip line, the traditional algorithm of time synchronization was analyzed, and the server-client mode was compared with the broadcast mode using multithread technology, then the present paper improved the broadcast mode to improve its precision. The new method can estimate total delay including clock offset and network transmission time. A simple, easy and little loading time synchronization method was designed for the distributed process control system of tandem hot strip line. The new method was applied in domestic some tandem hot strip line successfully which showed that it could meet the demands of process control system with little expenses, simple structure and high precision.