By using the concept of water right skewness and inverse calculating analysis,this paper made an inverse calculation of the water quantity concentrated from the tributaries to the main stream of the Tarim River during the period of 1957~2005,with the initial right as a scale,so as to correctly determine the real water quantity concentrated from the tributaries to the main stream and turning period of the initial water right skewness.Otherwise,the quantitative completion of the initial water right for the various tributaries was scientifically evaluated according to the range of positive or negative change of the skewness.