A new nano porous acetylcholinesterase (AChE) bioelectrochemical sensor was constructed based on gold nanoparticles (GNPs) and AChE modified self- made nano porous pseudo carbon paste electrodes (nano-PPCPE). The sensor was applied in the detection of marathon based on the representative inhibition mechanism between organophosphorus pesticide and AChE. The experimental results showed that the peak current of the sensor dramatically increased after adding gold nanoparticleas signal amplification. The best incubation time for marathon test was 14 min. The prepared AChE sensor was used to detect marathon. When the concentration of marathon was within the range from 1.0×10-10 to 1.0×10-13 g/mL, there was a good linear relationship between enzyme inhibition and the negative logarithmic of enzyme's concentration with the linear equation being I=19.43C-181.4, C=-lg(ρ/(g·mL-1)), the linear correlation coefficient being R=0.996, and the detection limit of 5.0×10-14 g/mL.