The power consumption of a variable optical attenuator (VOA) array based on a silica planar lightwave circuit was investigated.The thermal field profile of the device was optimized using the finite-element analysis.The simulation results showed that the power consumption reduces as the depth of the heat-insulating grooves is deeper,the up-cladding is thinner,the down-cladding is thicker,and the width of the cladding ridge is narrower.The materials component and thickness of the electrodes were also optimized to guarantee the driving voltage under 5 V.The power consumption was successfully reduced to as low as 155 mW at an attenuation of 30 dB in the experiment.