本文结合分布式海关条码监测系统项目的开发，详细介绍了S7-226 PLC 的通信机制与实现，指出应用其构造分布式监控系统的优越性。关键字:西门子PLC，激光条码扫描仪，分布式监控，通信Abstract: This article gives the principle and methods of SIMENS S7-226 PLC based on thedevelopment of distributed customs bar code monitoring and control system ,the communication machnism and realization of S7 226 PLC is introduced in detail. It indicates the excellence of application on PLC to build distributed monitoring and control system .KeyWords: SIEMENS PLC， Laser Bar Code Projection Scanner，Distributed Monitoringand Control，Communication