Abstract: In open-pit design and overall planning, it is the common methods that everyone delimit open-pit mining boundary through drilling stripping ratio contour. But in fact, there have some open-pit area cannot be developed economically which designated by the overall planning. In this article, first starting from the definition, then through the regulation of standard and some example, analyzed the importance of stripping ratio in open-pit mining design. Finally analyzed drilling stripping ratio have some limitations and should be taken seriously attention. The special cases in this article are important guiding for setting boundary of open-pit design and designating limits of overall planning.