Abstract: DTNB （Dithio-Bis（2-Nitrobenzoic Acid）） method was first established for determination of acetylcholinesterase activity by Ellman in 1961. Comparing with other methods, DTNB method is more convenient, rapid and sensitive for a large number of samples assay. DTNB method has been widly applied in research and clinical practice. In the present study, A micro colorimetric assay was first established for determination of butyrylcholinesterase activity in human liver. The catalytic property of BChE in human liver homogenate was also studied.