This paper studies the impact of LTPS (low temperature polycrystalline silicon) TFTs with fluorine implantation under NBTI (Negative bias temperature instability) stress. The fluorinated TFTs' devices can obtain better characteristics with samller threshold voltage shifts lower trap states and lower subthreshold swing variation. Therefore, the fluorine implantation does not only improve initial electrical characteristics, but also suppresses the NBTI-induced degradation.