Abstract: Based on the system model of the AMBs when it's rotor runs at high speed,a control method is investigated according to the multivariable model in this paper.As to the multivariable system model,a fuzzy decoupling method is used,and the valid fuzzy relation matrix with lower dimension is examined.The fuzzy decoupling method of the multivariable system with four-input variable and four-output variable is discussed,and the arithmetic method of the output variable is derived.And farthermore,the derivative of the input variable is taken into account,and the arithmetic method is derived as well.