Abstract: In order to study the reasonable support resistance of support in filling mining, the mechanical model of overlying strata movement in the filling mining by ultrahigh water material is built to analyze the relation between packed hydraulic support and surrounding rock, and the calculation method of packed hydraulic support resistance based on the mechanical property of the large size ultrahigh water material is obtained, which is already verified by engineering example in Taoyi Coal Mine of Jizhong Energy Group. Studies show that immediate roof will cave gradually with the advancing of the working face, while the main roof may keep stable structure without breaking at a certain range of hanging arch distance, and the pressure strength at the filling face is also low. Compared with ordinary longwall mechanized mining, lower support resistance of the filling mining of ultrahigh water material can not only meet the need of mining, but also guarantee the good filling effect.