Abstract: A knowledge-based variable-structure decoupling control strategy is developed and applied to the control of the nonlinear multivariable system so as to avoid the model-establishing process, especially avoid large amount of complex matrix operations necessary for the conventional decoupling control. Some modules in the knowledge base of this kind of control are described and its algorithmic main points are introduced. Strategies presented in this paper have been successively utilized in the homothermal control of a 3×3 strong coupled system a, three winding heater type standard temperature source, and an effect that the temperature stability and temperature homogeneity are better than 1℃ has been attained, which is impossible for the conventional control method.