A novel sensitive and elective electrochemical sensor was developed to detect methyl parathion (MP) based on a glassy carbon electrode (GCE) modified with gold nanoparticles ()/graphene nanocomposites film. The were modified onto graphene sheets using 4 as a reductant. The obtained /graphene nanocomposites were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical behavior of MP and interference studies were then investigated. Compared with metal ions and nitroaromatic compounds, which exist in environmental samples, the /graphene/GCE exhibited high adsorption and strong affinity toward MP. Under optimized conditions, the oxidation peak current of MP was linear to its concentration within the range of 4.0 × 10-7-8.0 × 10-5 M, with a detection limit ( = 3) of 8.5 × 10-8 M. These results indicated that the /graphene nanocomposites displayed a synergic effect involving the catalytic characteristics of graphene and nanocomposites, which can effectively improve the electrochemical properties of MP. Furthermore, the also enhanced sensor sensitivity to MP. Therefore, the /graphene/GCE could be a promising sensor for the fast, sensitive and selective detection of MP in real samples. The gold nanoparticles (AuNPs)/graphene nanocomposites are synthesized via the gold nanoparticles reduced on the surface of graphene, which are used to construct the AuNPs/graphene/GCE sensor. The electrochemical sensor was applied to detect methyl parathion. Under the optimized conditions, the AuNPs/graphene/GCE sensor shows a highly sensitive and selective detection of MP. [ABSTRACT FROM AUTHOR]