In order to solve the problems of lower nonlinear threshold optical peak power in fiber and more complicated coding algorithm caused by continuous pulse coding technique, a cyclic simplex coding technology and it′s application system in which the coding optical pulses were evenly distributed along the whole fiber were proposed. The comparative experiment adopting 27 km multimode optical fiber between traditional single pulse system and cyclic simplex coding system were made for validating the correctness of theory. The results show that compared to the continuous pulse coding,the cyclic simplex coding not only keeps same signaltonoise improvements to traditional single pulse technique, but also increasese nonlinear threshold optical peak power in fiber,and has more simple coding process in which it just transmits one row codes circularly, so the system can improve signaltonoise ratio and sensing range greatly in the same amount of measurement time. With this coding technology, the system attains ±1.5℃ temperature measuring uncertainty and achieves 3 m spatial resolution on 25 km of multimode optical fiber after 160 000 measurement times.