Aromatic hydrocarbons doped with K have been shown to be potential high-temperature superconductors. To investigate the doping effects of trivalent metals(Al, Ga, and In) that have a smaller radii than K, we studied the crystal structure, stability,charge transfer, band structure, and superconductivity of trivalent metal-doped phenanthrene via first-principles calculations.Doping with Al/Ga/In considerably differs from doping with K and cannot be simply regarded as a linear developmental change in the structural and electronic characteristics caused by a change in the valence electron numbers. Al/Ga/In atoms are difficult to dope into the intralayer region, and the charge transfer is close to zero, which is far less than the effect of K doping. We found that the metallization of the Al/Ga/In-doped system originates from the formation of gap states instead of charge transfer. The weak superconductivity obtained in the Al/Ga/In-doped system is also different from the K-doped system. These results are helpful in terms of understanding the structure and superconductivity of metal-doped aromatic superconductors.