A new type of Bi-based relaxor, Bi-2(Mg1/3Nb2/3)(2)O-7 (BMN), has been investigated to understand nature of relaxor behavior. The BMN thin films have been successfully fabricated by a sol-gel spin coating method on Pt/Ti/SiO2/ Si(I 0 0) substrate. Dielectric properties of BMN thin films were investigated in the temperature range of 20-750 degrees C at frequencies of 10(2)-10(7) Hz. The BMN thin film exhibits a characteristic diffused phase transition; the decreased dielectric constant and the increased dielectric constant maximum temperature with increasing frequency. The temperature dependent reciprocal dielectric constant (1/epsilon') deviates from the Curie-Weiss law in the temperature range over the dielectric constant maximum temperature (T-m). The diffuseness of the phase transition of BMN thin film was estimated by calculating the difference between T-m and T-cw (starting temperature following the Curie Weiss law). For BMN thin film, the Curie-Weiss temperature Theta, the Curie-Weiss constant c, the temperature T-cw and the temperature difference T-cw - T-m measured at frequency of 10(3) Hz are 912, 1.15 x 10(5), 969 and 49K, respectively. The dielectric relaxation obeys the Vogel-Fulcher relationship with the freezing temperature of 770K. (c) 2005 Elsevier B.V. All rights reserved.