Abstract: To study the main factors affecting the surface subsidence in shallow seam mining with thick unconsolidated strata, the orthogonal experiment method was used to rank the influencing degree of the three factors: bedrock thickness, unconsolidated strata thickness and mining thickness. The results show that bedrock thickness is the main controlling factor of the surface subsidence. It is concluded that ratio of bedrock thickness and mining height and ratio of bedrock thickness and overburden thickness are the key factors to determine the degree of surface subsidence and overburden failure. The comprehensive function expressions of the maximum subsidence value, coefficient of subsidence and influencing factors are given by regression analysis and fitting. The results are verified by engineering examples. The results show that the function expressions have high reliability.