Abstract: Open-pit limit optimization is an important content in open-pit mining design and production process control.Limit optimization requires that mine resource condition, mining technical condition, mineral product sales price, ore mining and processing cost be taken into integral consideration for the final realization of maximized economic benefit of mine production.Based on the 3D block model of mineral source, the paper describes the basic principle of floating cone method for limit optimization， and highlights the realization method of the limit optimization when slope angle changes in different space zones and the formation process of the open-pit limit under complex slope conditions.Finally, real cases of the application of floating cone method in mining softwares are presented.

Key words: Open pit limit optimization, Floating cone method, Spatial change of slope angle, Digital surface model, Block model