Abstract: In order to improve LANs’ reliability and transmission performance,the concept of parallel and fault tolerant LAN （P FTLAN） with dual transmission subsystem is presented in this paper.The function modes,technical features,and the hardware and software architectures of P FTLAN are given and some issues about its protocol implementation are described in details.The analysis results show that the scheme presented not only provides an effective approach to high reliable LANs,but also can improve their performance greatly.