Abstract: The overlying strata of working face was divided into three parts including soft stratum,key strata and alluvi- um. At the same time,the skewness subsidence model was built based on key strata theory to analyze the influence of all kinds of factors on skewness subsidence by introducing the concept of skewness subsidence level. In addition,the numerical model was used to analyze the effect of loosed bed thickness on earth surface skewness subsidence. The re- sults showed that the smaller bulking coefficient was,the more obvious the skewness level was;the smaller the distance from key strata to coal roof was,the more obvious the skewness level was;the larger the coal thickness was,the more obvious the skewness level was. When the length of goal reached a constant value,the skewness level remained un- changing;the larger the length of key strata was,the more obvious the skewness level was;the thicker the coal seam was,the more obvious the skewness level was. Also,the thickness increase of loosed bed can only make the subsidence continuity,but it cannot offset the skewness subsidence level.