Abstract: When the Rotary Cutting Drum for mining Cobalt-rich Crust is working on the fluctuant Microtopography,how to control the cutting depth and the cutting pose is a very crucial problem.The problem,that is,The optimal cutting position-pose of the Rotary Cutting Drum for mining Cobalt-rich Crust,is Modeled in this paper.The mathematic solution and the simplified solution are both provided in this paper.The modeling and analysis in this paper will supply some important reference to detecting the depth of the cobalt-rich crust and the fluctuant Microtopography of the cobalt crust.