A nanocomposite film modified electrode based on electrochemically reduced graphene oxide (ERGO) and polyoxometalate (POM) clusters was prepared. In this process, the Keggin-type heteropolymolybdate H4SiMo12O40 (SiMo12) was chosen as the representative POM. The POM/graphene nanocomposite film was constructed by electrochemical reduction of GO onto the Indium tin oxide electrode, which was used as matrix to form multilayer films by electrochemical growth method with SiMo12. The strong adsorption effect between the SiMo12 clusters and ERGO nanosheets induces the assembly of SiMo12 on ERGO in a uniformly dispersed state, forming a porous nanocomposite film. More importantly, the film modified electrode exhibited high electrocatalytic activities toward the reduction of S2O82- and NO2-. The enhanced electrochemical performances of (SiMo12/ERGO)(6) hybrids could be mostly attributed to the synergistic effect of ERGO and SiMo12 clusters. Considering the facile and environment-friendly features of this method, it is sensible as a general route for the incorporation of various types of POMs onto graphene matrices. This may allow the POM/graphene modified electrode for applications in the fields of catalysis and electrochemical sensor. (c) 2014 The Electrochemical Society. All rights reserved.