Abstract: The composite magnetic particulate composed of Fe3O4/Au/acetylcholinesterase (AChE) was synthesized and was absorbed on the surface of screen-printed carbon electrodes (SPCEs) coated with carbon nanotubes(CNTs)/nano-ZrO2/prussian blue (PB)/nafion (Nf)-membrane through magnet.A disposable organophosphorus pesticides (OPs) enzyme biosensor was developed for the determination of dimethoate.Different technologies were employed to study the construction process and electrochemical properties of the biosensor.In pH 7.5 0.1 mol/L KNO3 solution,the rate of inhibition (A) of the AChE by OPs was related linearly to the concentration of dimethoate in the range from 1.0×10-6 to 1.0×10-2 mg/L with a detection limit of 5.6×10-7 mg/L.The recovery was 88%-105% for chinese cabbage.The results of the analytical method were compaprable with that of gas chromatography method.The proposed biosensor has high surface activity due to the modification with composite nano-particles,rapid response,specific strong adsorption to OPs and was easily renew by removal of the magnet.It showed the merits of high sensitivity, disposabledesign,low consume of sample and portablity compared with other enzyme biosensors.This convenient,fast and sensitive voltammetric test method is suitable for the fast anlysis of OPs.