Abstract: A new zone axis (< 113>_c) has been provided to characterize the 1∶2 ordering structure of Ba(B′_1/3B″_2/3)O₃ (B′ = Zn²⁺, Mg²⁺, Co²⁺ or Ni²⁺, B″ = Ta⁵⁺ or Nb⁵⁺) perovskite by transmission electron microscopic (TEM) observation, and the corresponding atomic architecture of ordered perovskites has also been studied firstly. The 1∶2 ordering structure was revealed by the ±1/3112-type superlattice spots in the selected area electron diffraction (SAED) pattern. The corresponding high resolution transmission electron microscopic (HRTEM) image clearly displayed the ordering domain size and atomic structure. The composition contrast in HRTEM image matched well with the atomic architecture, further confirmed the 1∶2 ordering structure along < 113>_c zone axis.