Abstract: In order to study the laws of roof separation in gob-side entry retaining, a mechanical model was established on the basis of evolution mechanism of roof separation in gob-side entry retaining based on the elastic theory of beams. The analytic expression of deflection equation was determined through the principle analysis of superposition method; based on the mechanical model, we proposed a method to determine roof separation of anchorage zone, and further determined the anchor load effectively when the anchorage effect is equal to zero. 1025 working face in a mine roadway was taken as a calculation example, and the results showed that, the maximum roof separation value is 38 mm without the anchorage effect and the anchor load is 2.3 MPa when the anchorage effect is equal to zero; effective supporting scheme was provided, which combined with theoretical analysis and field conditions.