Epoxy is a key bond material in the mirror assembly of nested conical approximation Wolter-I type focusing telescope which is based on ultra-thin glass. The mechanical properties of the telescope is determined by the bonding strength of the adhesive layer with micron-scale thickness. The bonding strength of "ultra-thin glasses-F131 epoxy -graphite" bonding structure under different curing environments and surface roughness of graphite was studied. The results show that the bonding strength decreases with the increase of the curing humidity of epoxy and increases with the increase of the surface roughness of the graphite. The peel of the graphite was found to be the main type of failure in bonding structure by comparing the surface peeling area ratio of graphite. Finally, the B basis was introduced as an evaluation of bonding strength to improve the accuracy and reliability of the bonding properties for telescope assembly.