A novel variable optical attenuator based on buried polymer waveguides and waveguide bends is proposed. The attenuator consists of three waveguide sections, separated for waveguide bending by two embedded micorprisms. The attenuation of device was achieved by steering the beam propagation direction in the waveguide by thermo-optical effects. Detailed simulation results using the Beam Propagation Method are presented. In addition, radiation losses of the waveguide bends are experimentally investigated. After two-10¢X bends, the normalized insertion losses as low as 65.7¢H are obtained. The propagation loss of the buried waveguide is 0.47dB/cm at l=1.3 mm.