p‐Nitrophenol (PNP) has aroused much concern due to its high toxicity in industrial wastewater and drinking water. Herein, we designed a new plasmonic RuPd/HxMoO3–y catalyst synthesized by a simple impregnation method, followed by H2 atmosphere reduction. The synthesized RuPd/HxMoO3–y hybrid, having RuPd alloy nanoparticles (NPs) anchored on HxMoO3–y, namely hydrogen‐doped molybdenum oxide support, shows a strong localized surface plasmon resonance (LSPR) absorption peak at around 639 nm. Photocatalytic activity of Ru/HxMoO3–y hybrid for the reduction of PNP to p‐aminophenol (PAP) under visible light irradiation can be dramatically improved by alloying with Pd atoms. More importantly, a reasonable mechanism for PNP reduction is proposed. We find that synergetic effect between HxMoO3–y and RuPd alloy NPs of RuPd/HxMoO3–y plays a vital role in photocatalytic reduction, in which RuPd alloy NPs act as the active species and plasmonic HxMoO3–y acts as electron‐donation centre.