Inhibition of acetylcholinesterase (AChE) from head of honey bee (Apis mellifera L.) by organophosphate and carbamate insecticides was developed from Ellman reaction and analyzed by spectrophotometer at the wave length of 412 nm. The normal acetylcholinesterase activity from bee head was 33,645+-3,008 mUnit/g(protein) or 88.23 mUnit/bee head. Enzyme activity decreased 20 percent when grinded bee head was freeze-dried. Beside, enzyme activities of freeze-dried bee heads stored at 0 deg C and-20 deg C for 14 days were not significantly different. The result showed that low concentration of insecticides could rapidly inhibit enzyme activity. The minimum concentrations of ten organophosphate and two carbamate insecticides, methyl parathion, methamidophos, dimethoate, chlorpyrifos, dichlorvos, fenitrothion, trichlofon, diazinon, triazophos, phosalone, carbosulfan and carbaryl which could inhibit enzyme activity more than those of sensitivities (assigned at 11 percent) comparing with control were 0.0307, 2.9638, 4.1119, 0.0029, 0.0380, 0.0577, 4.7665, 3.4395, 0.0028, 0.2201, 0.0958 and 0.0350 ppm, respectively.