Abstract: When the range of observed scale is wide enough the Richardson curve of a map object always has a shape like an inverse 'S'.Considering this fractal character of map objects, this paper proposes a new method for determining the fractal non-scale interval of a map object.This new method substitutes an inverse 'S' mathematical model-Cubic Polynomial Model with Derivative for the original Richardson curve of a map object, and then establishes the mathematical formula for determining the non-scale interval on the basis of this mathematical model.Finally we tested the validity of the new method by some typical experiments, and the results of the experiments show that this method can work well.