Abstract: Mining design is a key link of mine construction and operation.In order to maximize economic benefits，resource condition，mining technical condition，mineral products price，ore mining and processing costs etc.should be considered in mining design.At present，the combination of 3D deposit model and mining design makes the mining design more simplified，and good dynamic effect is obtained.Taken a Liberian iron mine as an example，terrain model，solid model and block model of ore bodies are built by using 3DMine software.On this basis，mining designs including the open pit boundary optimization，development and haulage system and the stripping schedule are made，which directly reflect the mining plan and the data changes.Effect of different prices and steps on boundary optimization is discussed to analyze the variation under different stripping rate.In practical production，open-pit boundary can be adjusted according to the different situation to realize the best economic benefits.

Key words: Open pit mining, 3DMine, Mining design, Boundary optimization