Abstract: A multivariable decoupling generalized minimum covariance Self-tuning Controller,or STC,with Smith compensation,based on Chien's work,is presented in this paper.The proposed algorithms overcame disturbances between variables and realized static and dynamic decoupling and improved system stability.By introducing diagonal matrix decoupling method and Smith compensation simultancously,the design of STC can be used as SI/SO no-time-delay processses.Simulations and practical applications show that the STC developed in this paper has faster response and smaller overshoot.The results are quite satisfactory.