Abstract Using crystal structure prediction program (CALYPSO), we found many experimentally synthesizable low-energy structures with perfect or nearly perfect easy-axis magnetocrystalline anisotropy energy (MAE) in manganese nitride, including MnN, Mn2N, Mn3N2, Mn5N2, Mn4N, respectively, which are the more frequently studied stoichiometries by experimental researchers. MnN () shows giant MAE with values of E001=1006, E010=0, E100=920 μeV/atom (same hereinafter). Mn3N2 (P42/mmc) shows perfect easy-axis MAE, whose E010=E100=12, whereas Ibam has the nearly perfect easy-axis MAE with values of E001=324 and E010=345. Mn2N exists four almost totally perfect easy-axis MAE structures, including P4/mmm (E001=249, E100=250), Pccm (E001=E100=62), P4/nmm (E001=58, E100=60), Imma (E001=108, E100=109). Mn4N has one perfect structure I4/mmm (E001=E100=169) and two nearly perfect structures including Fmmm (E001=126, E010=121) as well as I4/mmm (E010=127, E100=133). Too many valuable structures are deserved to be further studied by both theoretical and experimental scientists about their other magnetic properties except the present MAE. The present study might attract close attention to these several compounds.