Summary: PID control schemes have been widely still used in process industries. However, the good control performance can not be obtained by simply using PID control schemes, since most processes are considered as multivariable systems with mutual interactions, time variation, and uncertain time-delays. In this paper, pole-assignment based self-tuning PID control system is newly proposed for multivariable systems whose system parameters and time-delays can not be exactly obtained beforehand. Then, the proposed PID control system is composed of a static decoupler, improved Smith compensators, pole-assignment based PID gain tuners and recursive parameter estimators. Finally, the effectiveness of the proposed control scheme is evaluated on a simulation example.