Due to the reversible transformation of physical property is strongly induced for ferro-fluid, so called intelligent working medium, subjected to the magnetic flux, its effective viscosity, especially, is closely dependent on the magnetization of ferro-particle and shows a special advantage in reducing the damping effect without magnetization hysteresis. Therefore magnetized fluid as a new engineering material, used for the shock absorber of building structure, has gradually attract scientist’s interest and engineer’s attention. Instead of previous experimental measuring the magnetized degree of ferro-fluid by costly Vibration Sample Magnetometer (VSM), a designed testing mechanism, based on modified Langevin function in apparent weight loss to characterize the magnetic behavior, is introduced in this study. It not only features as an stable, economical and affordable utility for local researchers, but a safe, easy operation with fast data acquisition would be also accessed. While compared with the experimental result conducted by VSM for ferro-sample provided by Matsumoto Co., the significant deviation using classic Langevin function in saturated magnetization Md ,within the magnetic field, 0 ~ 6 mT, can be effectively lessened to 50 % as the calculation undergone by modified model proposed.