The assembled domain structure model (ADSM) is applied to an analysis of thin film magneto impedance (MI) element. The ADSM is a multiscale magnetization model constructed by the assembly of mesoscopic particles called the simplified domain structure models. The ADSM successfully reconstructs the characteristics of the thin film MI element where three stable magnetic domain states coexist. The simulation reveals the influence of longitudinal distribution of magnetic field on the magnetization property that is hardly affected by the perpendicular magnetic field.