This paper investigates the stochastic mean square stability for the networked control systems with bilateral random network and packet dropout. Firstly, the stochastic characteristic of packet dropout is described as the Markov process,and the Markov jump systems with uncertain parameters are modeled by using the method of system augmented matrix. Then under the condition of taking into account the incomplete Markovian transition probability matrix, the necessary and sufficient criterias of stabilization are obtained based on the theory of Lyapunov stability and stochastic process. Simultaneously, the time varying controller is designed to guarantee the stochastic mean square stability of such systems. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.