Based on the density functional theory (DFT) method, we investigated the geometry stability, electronic and magnetic properties of vacancy-defected graphene with and without the adsorption of transition metal (TM) adatoms (V, Cr, and Mn). The results indicated that the appearance of vacancy, which broke the π-band, induced a magnetic property due to the unpaired electrons. After adsorbing the TM atoms, the electronic and magnetic properties were interestingly modified by the impurity states and the spin-polarized electrons of TM atoms. Moreover, the projected density of states (PDOS) results suggested that the magnetism of systems was mainly dominated by the 2p orbitals of C atoms around the vacancy and the 3d orbital of the TM adatoms.