There are many methods to compute index weight,AHP is one useful and convenient method of them.The paper introduces the main content of weight coefficient computing method based on AHP,and the step of root and sum of two judgement matrix disposal method.After the reasoning of the instance when the judgement matrix meet coherence condition,two conclusions are gained: it doesn't need do coherence verification;the finally weight coefficient is the judgement matrix's any column's unitary result.According to the conclusion and the AHP's principle,the paper discusses a convenient weight coefficient computing method and gives an example of applying.