Abstract: The relationship between control weight's bound and other parameters should be studied in predictive controller.For stair-like dynamic matrix controller,the relationship among the lower bound of control weight λ,the prediction horizon and stair-like factor is studied indirectly through a inter-variable.The lower bound is sensitive to parameters in some range,and a steep peak may appear.In these cases,the weighted control item in the objective function can be omitted,and the control moves are arranged by stair-like factor to improve the closed loop performance.The result can help to set the value of λ and simplify the algorithm.