The L10-ordered FePt films are promising materials for ultra high density magnetic recording media due to their high magnetic anisotropies. In this work, the L10-ordered FePt thin films are prepared by magnetron sputtering on CrW underlayer. A three-dimensional micromagnetic model, based on the symmetry of the L10 phase, is set up for FePt perpendicular media. According to the mismatch between the underlayer and FePt magnetic layer, a residual tensile stress is applied in the film plane. The simulated M-H loops accord well with the experimental results. The tetragonal crystalline anisotropy, especially high in-plane anisotropy, could enlarge the in-plane coercivity. The simulated perpendicular and longitudinal loops each have an open up in the tail, which is mainly due to the magnetostriction of the L10 phase.