The Belle II experiment at the SuperKEKB e+e- collider in KEK, Japan does start physics data-taking from early of 2018 with primary physics goal that is to probe the New Physics effect using heavy quark and lepton weak decays. During trigger and DAQ operation upon beam collision, it is important that Belle II detector status have to be monitored during data-taking against an unexpected situation. Slow control system, built in the Control System Studio (CSS) which is a GUI window design tool based on Eclipse, is one of monitoring systems in Belle II operation. NSM(Network Shared Memory) is a core technique of slow control system which make it possible for all systems connected to belle II server share data. With NSM, database and archiver servers are connected to slow control system. Experimental parameters are downloaded to Belle II main database server which is based on PostgreSQL. Real-time results are stored in archiver server which is based on EPICS(The Experimental Physics and Industrial Control System) archiver appliances and tomcat which is open-source java servlet container. In this study, we report the development of slow control system for the Belle II electromagnetic calorimeter (ECL) trigger system.