In view of the problem of the opposite judgement in AHP, a new method of judgement for the consistency of group decision by using fuzzy relation matrix is offered and the consistency of group decision is also classified. When the classification is in consistency, the judgement for the matrix is proved fair. By testifying the feasibility of the method through practical examples, a new algorithm for opposite judgement in AHP defines a new consistency coefficient. The result is proved to be in consistency with the findings in correlate reference through practical examples.