Remarkable magnetic anisotropy provides more possibilities in electronic devices such as quantum information storage and processing. Here, based on first-principles calculations, we identified a series of magnetic adatoms including 12 d-type and 8 p-type members with estimated high structural stability and large magnetic anisotropy energy (MAE). Among the p-type systems, a giant MAE up to 157 meV was predicted for the Pb adatom with out-of-plane magnetization and up to 313 meV for Bi with in-plane magnetization. By analyzing the density of states and the p-orbital-resolved MAE, the large MAEs are found to mainly derive from the orbital hybridization of degenerated px/y near the Fermi levels, which is induced by the synergistic effect of the ligand field and significant spin-orbit coupling interaction. In addition, by comparing various magnetic configurations of Pb/Bi atomic kagome/hexagonal/triangular magnetic lattices, we found that their magnetization keeps the same direction as that of the single Pb/Bi adatom, which further confirms the robust magnetic anisotropy of the individual Pb/Bi adatom on the graphane surface. Our findings provide a promising platform for the realization of atomic scale memory.