Based on molecular dynamics simulation, the effects of vacancy location, shape and atom deletion rate on Young's modulus of graphene were investigated. The results show that the position of single vacancy defect has a certain effect on Young's modulus of graphene, and when the applied stress direction is the same as the cross-section direction of the edge vacancy defect, the Young's modulus of graphene decreases less with the edge vacancy defect than with the middle vacancy defect. It is also found that the Young's modulus of graphene decreases with the increase of atom deletion rate due to mapped transverse long strip vacancy defects, mapped longitudinal long strip vacancy defects, mapped circular hole vacancy defects and random vacancy defects. For mapped circular hole vacancy defects and random vacancy defects, the decrease of Young's modulus of zigzag graphene is similar to that of armchair graphene. For the mapped transverse and longitudinal strip vacancy defects, the decrease ranges of the Young's modulus of zigzag and armchair graphene are quite different, which is related to whether the orientation of chiral vector of graphene is consistent with that of strip vacancy defect.