The high magnetocrystalline anisotropy energy (MAE) materials are extremely vigorous for the information storage. Based on first principle calculations, we found the MAE of metallophthalocyanine (MPc) is greatly changed by adopting halogen atoms due to the strong interaction between metal and halogen atom. The influence of the interaction is also related to the bond length between the halogen and metal. Finally, the variation of the bond length d(W-Cl) can be realized by applying external electric. This study provided guidance for modulating the MAE for 2D magnetic films for the practical applications.