Abstract: It was to evaluate the ecological security and establish the regular use of fipronil 8% SD in corn and soil, field experiment was conducted to reveal residual degradation dynamics and the final residues of fipronil 8% SD in corn and soil. The residues of fipronil in corn and soil were determined by Agilent 7890A GC equipped with ECD, and application safety was assessed. The degradation dynamic test results showed that the half-live of fipronil in soil was 2.7-3.9 d, more than 89% degradation at 14th day after application, and the half-live of fipronil in corn was 2.2-4.3 d, more than 78% degradation at 9th day after application. The final residue tests showed that the final residue of fipronil were lower than 0.01 mg/kg in samples, CAC provided the maximum residue limit of fipronil in corn was 0.01 mg/kg. An 18.75 g/kg preparation (active ingredient 1.5 g/kg) corn seed was recommended for fipronil 8% SD in seed dressing to control grubs before corn seeding.