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In the mining process of underground coal, the bed separation of overlying strata is inevitable. The developing process of the bed separation has an important influence on mining subsidence. It is very significant to study the developing regular patterns of the bed separation for understanding and perfecting the mining subsidence theory further. In this paper, Realistic Failure Process Analysis (RFPA) is used to research the distributing patterns of mining induced bed separation of overlying strata. The strata are sedimentary coal strata. And the similar material simulation experiments are used to test the results. The study shows that the growing height of bed separation is increasing as the advance of working face. At the beginning of coal mining, the height of bed separation increases slowly. As the distance of advance increases, the growing rate of separation height becomes faster gradually. After the working face advances a certain length, the growing rate of separation height decreases and closes to zero. After arrive a limit height, the growing height of bed separation will not increase after arriving a limit height. At last, the bed separation will distribute in a range of trapezoid with a 60 degree bottom angle above the goaf.