The ranking method of interval grey numbers is researched. Firstly, the merits and demerits of the existing methods are analyzed. Then, in order to suit the actual application, based on grey numbers’ universe of discourse and the principle of information persisting, the projection rule from ordinary interval grey numbers to standard grey numbers in universe of discourse [0,1] is designed. Moreover, the concepts of relative kernel and degree of accuracy are proposed aiming at the standard grey number. Based on these concepts, the ranking method of grey numbers is presented, which overcomes the shortages of existing ones. The discriminations among the same grey numbers in different application background are different, which are conductive to analyze for decision makers. Finally, examples show the feasibility and superiority of the proposed method.