This paper presents an QoS (quality of service) based control system of teleoperation via the Internet. Quality of service on the Internet refers to a set of quality requirements on the performance of the data transmission necessary to achieve the required functionality of an application. The quality of data transmission via the Internet is measured or reflected by a set of QoS parameters. Since the stability of the teleoperation system is sensitive to the data transmission quality of the Internet, it is important to adjust the control strategy of robot systems in teleoperation based on the quality (reflected by measured QoS parameters) of the network for data transmission. One of the widely used QoS parameters is network delay. This paper proposes a robot controller gains adjustment scheme based on QoS parameters (network delay) measured using a quadratic programming approach. Moreover, a teleoperation experiment is presented to demonstrate the effectiveness of the proposed controller gains adjustment scheme.