This paper presents a systematic design method of internal stable decoupling of multivariable systems on state space. First, internal stable decoupling by state feedback is presented for systems with unstable row zeros. Second, unstable zeros which are not row zeros are considered and the internal stable decoupling method is proposed by combining the above method and the compensator. Third, these decoupling methods are applied to decoupling by inverse system. In particular, the inverse system for unstable non-row zeros is presented by modifying the compensator.