Abstract: In order to solve the problem of timing of roadway-side support, the structure of surrounding rock in gob-side entry retaining was analyzed, the analysis showed that the three hinged girder structure of the basic roof of retained roadway was the key factors of the deformation of surrounding rock in gob-side entry retaining, and combined with the given deformation of surrounding rock in gob-side entry retaining to study the timing of roadway-side support, it's proposed that roadway-side support should adapt to the given deformation of surrounding rock of roadway, especially the given deformation of roof movement. Judging the situation of the basic roof contacting with coal gangue was needed to determine the timing of roadway-side support through monitoring the quantity of roof falling. The numerical simulation method was applied to assess the rationality of roadway-side support time in the process of gob-side entry retaining of Shenhuo group Xuehu coal mine, the result showed that when the roadway-side support lagged 10 m distance after working face, the support effect was good, and the best timing of roadway-side support was that the roadway-side support lagged 25 m distance after working face, these results could be used to provide technical support in site construction of gob-side entry retaining to the mine.