Abstract: For the uncertain time-variant linear model of voice coil motor in micro hard disk servo control system,a nonlinear observer and its corresponding feedback controller with one saturation term are proposed by utilizing Lyapunov stability theory and linear matrix inequality.Theoretically,by means of the designed controller,the system is globally uniformly ultimate bounded,and disturbance attenuation is achieved.Multiple kinds of disturbances are used to examine the controller and the results show that the output of the slider head can rapidly enter into the admi-ssable scope of the specific magnetic track and maintain within the scope.Furthermore,fast disturbance attenuation can be achieved with the controller.