Abstract: The structure of oriented domains in colossal magneto-resistance material La0.7Ca0.3MnO3 (LCMO) was investigated by transmission electron microscopy(TEM) and high resolution electron microscopy (HREM). Electron diffraction verified that LCMO presents just a single phase with an orthorhombic symmetry which meets the extinction conditions: 0kl, k+l=2n+1; hk0, h=2n+1; h00, h=2n+1; 0k0, k=2n+1; 00l, l=2n+1, with no other phases observed. The oriented domains in LCMO crystal have two kinds of typical morphologies, i.e., formless and wedge ones. HREM results showed that the domain boundaries are almost diffuse and consist of some interfaces with low energy and high index.