The hydraulic support is the key equipment of the residual coal stoping working face, which provides the safe working space and the wind circulation channel for the remining. Scientific mining of residual coal is on the basis of the optimization of hydraulic support structure and working resistance. The Hydraulic Support Optimization (HSO) is mainly influenced by geological factors, including seam thickness, dip angle, roof rock fracture structure, especially the Roof Caving Zone (RCZ) distribution. The contribution of this paper lies in HSO of 3101 residual coal sublevel caving face at Shenghua Mine, with the combination of physical simulations, theoretical analysis, and field measurements. Influenced by forward RCZ and sudden instability of coal pillars, the main roof across the caving areas fractured and caused rotary instability towards the goaf. The hinged roof structure of "long key blocks across the caving areas" was thus formed, which resulted in the mutagenic increase of support working resistance. Reasonable working resistance and structure of the support under such conditions were obtained, and the conduction of pre-grouting solidified the roof in the caving area and reinforced the coal pillars, thus enhancing the bearing capacity.