This paper is concerned with the problem of teleoperation systems over networks. As is well known, quantization and time delay are unavoidable in computer network communications. Compared with previous work, we consider both of them when analyzing such systems. The controller used in this paper is proportional-derivative(PD) controller, but the output signals of master and slave systems are quantized before being transmitted. New criteria are presented to show that the controller can stabilize the master-slave system under variable time delay and quantization. Finally, simulations are given to demonstrate the effectiveness of our results.