Abstract: To analysis the existing determined method of the roof span and the applying of energy release rate,this paper use energy release rate to calculate span is the innovation,base on the beam model analyze the feasibility and put forward the concept of surface energy release which suitable for analysis the stability of mining roof.According to the surface energy release calculation and get the formula of roof limit span and safety thickness,it’s non-linear relationship between roof limit span and safety thickness with modulus of elasticity,buried depth.To proving it by comparing with the practice engineering,and applied to calculate the stope limit span of the eastern mine area in Tiao-Shui River phosphorite,and the result is reasonable.