A brief introduction on system composition of Jiangsu Grand Canal monitoring control system for regime of flow is given in the paper,and the emphasis is puton the upper computer softwareCitect.Citect is a sophisticated SCADA software in the industrial control domain with powerful functions inclucling I/O processing,data acquisition and processing,and its best advantage in the complete support of computer network.In this system,Citect can control the normal operation of the whole system,and at the sametime,it provides a manmachine interface for operational personnel to browseand inquire monitoring data and issue control instructions.