$E^{rns}$ is an envelope glycoprotein of classical swine fever virus (CSFV) and has an unusual feature of RNase activity. In the present study, we demonstrate that $E^{rns}$ counteracts Newcastle disease virus (NDV)-mediated induction of IFN-$eta$. For this purpose, $E^{rns}$ fused to the enhanced green fluorescent protein (EGFP) was transiently expressed in porcine kidney 15 (PK15) cells. In luciferase activity assay, $E^{rns}$-EGFP was found to prevent IFN-$eta$ promoter-driven luciferase expression and block the induction of IFN-$eta$ promoter mediated by NDV in a dose-dependent manner. Through IFN-specific semi-quantitative RT-PCR detection, obvious decrease of IFN-$eta$ mRNA in NDV-infected PK15 cells was observed in the presence of $E^{rns}$-EGFP. In contrast, EGFP alone showed none of this block capacity. In addition, $E^{rns}$-EGFP mutations with RNase inactivation were also found to block NDV-mediated induction of IFN-$eta$. These evidences establish a novel function for CSFV $E^{rns}$ glycoprotein in counteraction of the IFN-$eta$ induction pathway.