本文以Quantum 系列PLC 为研究对象，研究了其支持的通信协议。并且以Modbus 协议为应用层协议，TCP 协议为传输层协议，IEEE802.3 为介质访问控制协议，结合VC++6.0 里的Winsock 网络编程控件，编制了Modbus/TCP 通信程序，实现了Quantum 系列PLC 与监控制站之间的以太网通信。该程序具有通信速度快，可靠性高的特点。关键词: 协议；Modbus 协议；TCP 协议；套接字； PLCAbstract: This article introduces a kind of communication based on the Quantum series PLC. Using protocol of Modbus as protocol of application layer、 TCP as protocol of transport layer 、IEEE802.3 as protocol of MAC, through Winsock of VC++6.0 ,realize the Ethernet communication between Quantum PLC and monitor platform. The system that has this control system can become more speediness、economic and reliable in communication.Keyword：protocol；Modbus protocol；TCP protocol；Socket；PLC