Abstract: Based on the Smith precompensation technique and the decoupling robust theory, this paper studies the robust stability of multivaliable system with time delays and derives the general conclusion that under the condition of Smith precompensation matching strictly, if the closed-loop system is stable and its perturbed system is robust diagonal dominance, the perturbed system must be robust stable. This result has the theoretical significance for resarch on the relation between system structure and its robustness, and also contributes the theoretical basis to robust design for the multivariable systems with uncertainty and time delays.