Abstract: Herein the fluorescent-labeled ligand and the molecular simulation method were used to study the interactions between the γ-aminobutyric acid (GABA) receptor of the insects and fipronil. The fluorescence labeling experiment results showed that strong interactions were existed between fipronil and the GABA receptor in the brain of the housefly. The maximum number of binding siteRT and the equilibrium dissociation constants (Kd) were (21.3±2.5) pmol/mg protein and (109±9) nmol/L, respectively. Furthermore, the molecular simulation results also suggested that there were some strong hydrogen bond interactions between fipronil and the RDL receptor of the fruit fly. In addition, the CDOCKER interaction energy between them was-137.93 kJ/mol. The above results clearly illustrated that the fipronil has strong affinity on the GABA receptor of insects and high toxicity to insects.