Input-output decoupling is well-known to be effective in the control of the nonlinear systems. This paper points out some problems of this technique in applications, and obtains a new digital input-output decoupling feedback law by using the inherent structure of the system. The effectiveness (accuracy) of our new control technique are confirmed by simple computer simulations. Finally, a digital compensator is also designed. The problems we study are of importance in the field of nonlinear control of robots, aerospace navigation, and vehicular control. The methodology to be employed involves both algebraic and geometric aspects of the systems.