We propose a pre-electrical bias aging to reduce threshold voltage (Vth) shift of hydrogenated- amorphous silicon thin-film transistor (a-Si:H TFT) for AMOLED display. The quantity of Vth shift in the sample subjected to a bias-aging is reduced due to the reduction of created dangling bond density, compared with a sample without a bias-aging. When an identical stress duration of 50,000 sec is applied to a-Si:H TFT with or without a pre-electrical bias-aging, the created dangling bond density (ΔNDB) after a pre-electrical bias-aging is decreased from 1.38 × 1011/cm2 to 0.685 × 1011/cm2. Our experimental results indicate that after the pre-electrical bias aging, a newly created dangling bond during an electrical stress is decreased because a weak bond density and hydrogen diffusion may be decreased.