Abstract: Acetycholinesterase( ACh E) was extracted from chicken brain by aqueous two- phase,and its enzymatic characteristics was studied.The result showed that the most optimum conditions of chicken brain ACh E were 37 ℃and p H7.5,Km5.67 × 10^-5mol·L^-1,Vm0.20 × 10~2mol·( min·L)^-1,indicating its more affinity to the substrate,compared with commercial ACh E. Its sensitivity to carbamate was studied. The result indicated that the 50%inhibition concentration of five carbamate toxins( carbofuran methomyl,carbaryl,aldicarb,metolcarb) were 0.004,0.07,0.23,0.53,5.24 μg·m L^-1,and the bimolecular rate constants were 40.89 × 10~5,3.09 × 10~5,2.80 × 10~5,2.78 × 10~5,2.74 × 10~5L·( mol·min)^-1.These results proved that the ACh E extracted from chicken brain was more sensitive to carbamate toxins and had the advantages of low cost,high activity and simple preparation. The ACh E extracted from chicken brain showed its great siginificance in carbamate toxins residue detection.