Unlike traditional gas-liquid-solid microreactors with the catalyst coated on the inner wall, a gas-liquid-solid monolithic microreactor with the Pd nanocatalyst coated on the polydopamine modified nickel foam was developed in this study. This new design enables large surface area for loading the nanocatalyst and enhancement of mass transfer. The performance of the proposed monolithic microreactor was evaluated by hydrogenation of nitrobenzene. It was found that this monolithic microreactor displayed more excellent performance than conventional flat microreactor. Meanwhile, the effects of the nickel foam length, liquid flow rate, gas flow rate and inlet nitrobenzene concentration on the nitrobenzene conversion, aniline concentration at the outlet and gas conversion were also studied. Experimental results showed that the increase of the nickel foam length and gas flow rate and the decrease of the liquid flow rate could improve the performance. Besides, although increasing the inlet nitrobenzene concentration could result in the increased aniline concentration at the outlet and gas conversion but the nitrobenzene conversion was decreased. This work opens a new window for the design of high-performance gas-liquid-solid microreactor toward multiphase catalytic reactions.