The H ∞ control problem for networked control system with data packet dropout in both S-C link and C-A link via observer-based controller is researched in this paper. Firstly, the networked control system with data packet dropout in both S-C link and C-A link is modeled as a discrete Markov jump linear system. Secondly, the sufficient and necessary conditions on the stochastic stability of the closed-loop system is established, the solution method of the controller and observer gain matrix are also given on condition that the transition probability matrix is completely known and partly unknown, respectively. The minimal disturbance suppression performance index is also obtained. Finally, two simulation examples illustrate the validity of the proposed method. INDEX TERMS Markov jump system, data packet dropout, observer, stochastic stability, closed-loop system. WEI WEI (Senior Member, IEEE) received the M.S. and Ph.D. degrees from Xi'an Jiaotong University, Xi'an, China, in 2005 and 2011, respectively. He is currently an Associate Professor with the School of Computer Science and Engineering, Xi'an University of Technology, Xi'an. He ran many funded research projects as a Principal Investigator and a Technical Member. He has published around 100 research articles in international conferences and journals. His current research interests include the area of wireless networks, wireless sensor networks, image processing, mobile computing, distributed computing, and pervasive computing, the Internet of Things, and sensor data clouds. He is a Senior Member of the China Computer Federation (CCF). He is an Editorial Board Member of Future Generation Computer System,