Aqueous/organic two-phase CO selective reduction of nitroarenes catalyzed by the thermoregulated phase-transfer catalyst Ru-3(CO)(9)(PEO-DPPSA)(3) (PEO-DPPSA: poly(ethylene oxide)-substituted 4-(dipbenylphosphino)benzenesulfonamide) was investigated. The influences of reaction temperature, CO pressure, ratio of substrate/catalyst (mol) and organic/aqueous (vol.%) on the reduction were studied. Under the condition of 140degreesC, P-CO = 4 MPa and 10 h, the conversion of o-ClC6H4NO2 was 97.5% and the selectivity of the desired amines was higher than 99%. The reduction proceeded with good activity and selectivity toward nitro group when halogen, carbonyl or cyano groups where present in the substrates. The catalyst in the water phase could be recycled three times with little loss of catalyst activity.