Recent advances in sensing technology and networked communication are leading to the emergence of Wireless sensor networks (W). They have greatly facilitated and enhanced the automated, remote, and intelligent monitoring of a large variety of physical systems. Recently, wireless network application has been extended to Wireless Sensor-Actuator Network (WSAN) to control processes with Real-Time loop. A WSAN is a distributed system of sensors and actuators that are connected over wireless links. Decrease in wiring costs, facility in installing and maintenance, increase in scalability and possibility of controlling geographically distributed systems, are some of important advantages of these systems. Although, they are facing with some serious challenges such as delays, packet loss in transferring data and packet congestion in networks. In this thesis, modeling, stability analysis problem and real-time controller design using WSAN are addressed. IEEE 802.15.4 as most appropriate protocol is considered for networks communication. In the first step, the transmission algorithm of IEEE 802.15.4 has been studied and using the results of this, wireless networked control system has been modeled in presence of delay and pocket loss in the both network between sensors and controller and network between controller and actuators. Then, with construction of an appropriate Lyapunov-Krasovskii functional, sufficient condition for mean square asymptotically stability of the closed-loop wireless networked control systems is derived, and based on this, a feedback controller design procedure is proposed for stabilization purpose. In order to compensate adverse effects of non-idealities of communication network in sensors and controller connection, the use of an estimator is proposed and the estimation algorithm is presented. The estimator is formulated as a Time-dependent Impulsive System. Then, by using these models sufficient condition for mean square asymptotically stability analysis of closed loop system and estimator is proposed. Finally, in order to increase freedom to compensate the communication constraints, a switching controller is designed where the feedback gains change with respect to different network conditions. For this purpose, sufficient condition based on Linear Matrix Inequality, for mean square asymptotically stability of Wireless network control systems has been suggested. Key Words: Wireless Sensor-Actuator Network (WSAN), Networked Control System (NCS), mean square asymptotically stability, protocol of IEEE 802.15.4, Lyapunov-Krasovskii functional, Linear Matrix Inequality, Compensate Delay and Packet Loss