This paper proposes a hybrid observer scheme for power systems by exploring the special features of the nonlinear power system model. Rather than directly applying the existing nonlinear observer theory to the 6/sup th/ order nonlinear power system model, the model is first decoupled into a 3/sup rd/ order nonlinear subsystem and a 3/sup rd/ order linear subsystem. Low order observers are designed for each subsystem separately. The proposed observer scheme is much simpler in implementation than a 6/sup th/ order nonlinear observer which is obtained by direct applying nonlinear observer theory. Simulation results show that this hybrid observer can estimate the state of a power system with good transient response and zero steady state error.