In this paper, the authors have adopted the synthetic appraising model based on multi-attribute to select mining methods. They at first have deduced the boundary weigh coefficients of the sequencing variety about all the plans when weigh coefficients of arbitrary two norms are relatively varied considering the variation of appraising norms. Secondly, the value of boundary norm based on single norm variation is given after the sequencing of all the plans changes. At last, the valid range of optimal value is calculated by the analysis of sensitivity.