Abstract: Based on the introduction of diameter difference between borehole and rockbolt in the combined supporting at home and abroad,the stress and deformation of resin capsule under the conditions of different annular thicknesses and uneven thicknesses on the left and right sides due to decentration of rockbolt was analyzed with numerical simulation,and the rationality of three diameters matching was verified,and the supporting system might be unstable because of the uneven stress of resin capsule caused by decentration of rockbolt.Diameter difference between borehole and rockbolt should be controlled reasonably,and bolts should be placed in the middle of boreholes,good supporting effect could be achieved.