The acetylcholinesterase (AChE) activity of cerebral ganglion from white shrimp (Litopenaeus vannamei) was determined by the improved method of ELLMAN. On the basis of suitable conditions for determination, the AChE activities of other tissues were determined. This study also compared the effects of chlorpyrifos, dichlorvos, phoxim and acephate on AChE activity in cerebral ganglion. The results showed that the highest activity of AChE was obtained at temperature of 35 ℃ and pH value of phosphate buffer solution of 7.5, while holding time had little effect on the AChE activity. The difference of AChE activitiy in different tissues from white shrimp was obvious. The AChE activity of cerebral ganglion was 49.73±8.42 nmol/(min·mg)protein, which was 3 times, 15 times and 19 times higher than that of gills, muscle and hepatopancreas, respectively. AChE was most sensitive to dichlorvos(IC₅₀ =0.19 μg/mL) and sensitive to chlorpyrifos(IC₅₀=7.20 μg/mL) and phoxim (IC₅₀=9.39 μg/mL), but was less sensitive to acephate (IC₅₀=136.77 μg/mL). This shows that the shrimp culture should prevent the toxicity of organophosphorus pesticides, such as dichlorvos，chlorpyrifos and phoxim.