Abstract: NCS(Networked Control System) is a kind of feedback control systems where the control loops are closed through real time control network. The existence of real time network in the feedback control loop makes analysis and design of an NCS complex. Conventional control theories must be reevaluated before they can be applied to NCS. Numerous research papers have investigated analysis and design of NCS from different views. This paper aims at introdution state of arts of NCS and points out the field of further research.