The solution NMR (P-31 and H-1) and FTIR spectroscopies were employed to investigate the structure information of water-soluble complex HRh(CO)[P(m-C6H4SO3Na)(3)](3) (1) [P(m-C6H4SO3Na)(3): trisodium salt of tri-(m-sulfophenyl)phosphine, TPPTS] supported on SiO2 (1/SiO2). The P-31(H-1) NMR spectra showed that a pair of new twin-peak at about 31.5, 32.1 ppm while no typical twin-peak at 44.0, 44.7 pptn for the phosphorus species ascribed to the complex 1 were observed at 1/SiO2. However, the typical phosphorus peaks for the complex 1 appeared in the case of using TPPTS or Na2CO3-preimpregnated SiO2 as supports. Moreover, the immobilization caused a considerable oxidation of the liberated TPPTS to OTPPTS (OTPPTS, i.e. OP(m-C6H4SO3Na)(3): trisodium salt of tri-(in-sulfophenyl)-phosphine oxide) species as evidenced by P-31(H-1) NMR spectroscopy. The phosphorus-31 peaks at 31.5, 32.1 ppm at 1/SiO2 were found to be unchanged before and after the propene hydroformylation. The FTIR results revealed that the CO band appeared at about 1870 cm(-1) for the 1/SiO2 catalyst, which was lower than that for the precursor complex 1. It is concluded that there exists a strong interaction between the complex 1 and the acidic support of SiO2, resulting in the deformation of the Rh-phosphine complex containing less than three TPPTS ligands, which further transformed by dehydrogenation and dimerization under evacuation to form a species likely [Rh(CO)(TPPTS)(2)](2) as a main surface complex species at the catalyst 1/SiO2.