The GUI of the control system of HIRFL adopts Control System Studio(CSS).CSS is a collection of tools:CSS BOY,Alarm handler,archive engine,as well as several operators interface and control system diagnostic tools.Most of the tools deal with Process Variable(PV)in different ways.For example,CSS BOY displays the value of a PV;alarm concentrates on the alarm state of a PV.Each individual tool deserves some attention,and the Experimental Physics and Industrial Control System(EPICS)toolkit,indeed offers each functionality as a separate tool.A key point of CSS is the integration of such functionalities.All the work are completed under the platform of CSS.