Fourmonodentate P-ligands and their mixtures (six groups of double-ligand systems, four groups of triple-ligand systems and one group of tetra-ligand system) were used with Rh(acac)(CO)(2) (acac = acetylacetonate) or Rh (acac)CO(PPh3) as the catalyst in the hydroformylation reaction of 1-butene. It was found that different Rh catalysts showed little difference in the catalysis performance. The general order of catalysis performance is double-ligand system > single-ligand system > triple-ligand system > tetra-ligand system. Some synergistic effect in the double-ligand system was detected which needs a further investigation. (c) 2017 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.