The magnetic microstructure of the L10 FePt perpendicular magnetic film, grown epitaxially on MgO substrate, was studied using high-resolution electron holography. It was shown that the hologram-fringe information of stray-fields can be used to determine the sense of stray-fields and thus, the sense of perpendicular magnetizations inside the film. Furthermore, we were able to directly reveal the detailed perpendicular magnetic structure of L10 FePt epitaxial film by constructing unwrapped phase-image and induction mapping. The perpendicular induction-strength was varying with the domain size. The variation of induction-strength was due to a variation of the degree of ordering in the weakly ordered film. (C) 2012 American Institute of Physics. [doi:10.1063/1.3677649]