The calculation on working resistances of supports has been one of key research questions for coal faces with sublevel caving. Based on experimental results of mechanical property of top-coal, it is the top-coal failure strength meeting Mohr-Coulomb Theory that is summed up. According to force characteristic of top-coal body in coal face with sublevel caving, using strain-equivalent principle of Damage Mechanics, the authors set up bearing mechanical model for top-coal body within face width. From the top-coal bearing capacity point of view, the interaction relationship between supports and top-coal body is studied. Theoretical calculation formula on working resistance of supports is deduced. Ground press behaviors which working with resistances of supports are increased with top-coal strength increment were better explained with this model. The conclusions have a definite direction value for calculating working resistances of supports in coal faces with sublevel caving.