In order to obtain the machining requirements of the machining features, it is necessary to develop a proper fixture locating scheme to constrain correctly the degrees of freedom (DOFs) of a workpart. In this paper, a machining-requirement-based design approach to locating scheme is for the first time created. Firstly, the relationship is established between the machining dimensions and the DOFs to be constrained theoretically. Secondly, the fixture locating scheme is established to characterize practical constrained DOFs of a workpiece in terms of the locator number and positions. As a result, locating correctness is defined according to the relationship between the theoretical constrained DOFs and the practical constrained DOFs, and then the determination algorithm of locating parameters is proposed quantitatively for the first time to design the fixture locating scheme.