In this paper a new state observer is proposed to estimate the minimum phase state contained in objects with long delay time. The minimum phase state of the object can be controlled with two degree of freedom which have the stable closed-loop and the input-output response designed. The combination of the minimum phase state observer and the two degree of freedom controller can accomplish both the regulated disturbance and the relatively high speed input-output response. Simulations of numerical examples are shown in comparison to the modified Smith predictor.