This paper investigates the synchronization control problem for teleoperation systems with time-varying delays base on generalized extended state observers (GESO). The proposed controller ensures the stability of the teleoperation system as well as synchronization of positions of the master and slave manipulators. By feedback linearization, the nonlinear dynamics of the teleoperation system is transformed into a new state space model about tracking errors and time delay. Then, the GESO and the control law are designed for the multiple input multiple output model with mismatched uncertainties, and the GESO is able to estimate the uncertainties induced by the time-varying delay and other disturbance. Moreover, the stability and disturbance analysis are also presented for the teleoperation system. Finally, simulations are provided to verify the effectiveness of the proposed control method.