In this study, a novel Prussian blue (PB), ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and graphite felt (GF) nanocomposite electrode (PB/[Bmim][BF4]-GF) was obtained by simple methods involving GF placed in a ultrasound bath of [Bmim][BF4] and then in a PB precursor solution. The electrode showed an efficient activity for electrocatalytic detection of nitrite. [Bmim][BF4] was ultrasonically immobilized on GF, and played two roles in the fabrication of the electrode: (1) enhancing the synthetic rate of PB from a K3[Fe(CN)6] and FeCl3 solution; (2) anchoring PB nanoparticles on the surface of the GF. The PB/[Bmim][BF4]-GF electrode was characterized by scanning election microscopy (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD) and electrochemical methods, respectively. The as prepared PB/[Bmim][BF4]-GF electrode exhibited a rapid response of less than 2 s, a very high detection sensitivity of 3.5 A mol−1 L, a low detection limit of 1.3 × 10−8 mol L−1 as well as excellent stability and selectivity.