Under the weighted majority rule, when voting individuals make a decision to choice one of two alternatives (or candidates), the individuals' power can be measured by two methods which are Shapley Shubik's power index and Banzhaf's power index. But these two methods can't measure the individuals' power when the individuals make decision to choice one of alternatives (or candidates) between three or more alternatives (or candidates). But by establishing a measuring model to calculate the difference of the the two group preferences and transforming this measure into the calculation of the shortest way on the nondirective graph，a method to measure the voting individuals’power under the weighted majority rule is proposed wbe ther the indiv[duals make a decision to choice one of two alternatives(or candidates)or to choice one of alternatives(or candidates)between three or more alternatives(or candidates)．And then an analysis example is given．