Paramagnetic (Co3O4)x/3(TiO2)1- x(03O4 and TiO2 from 700 ℃ to 1000 ℃ in air. X-ray diffraction (XRD) re sults showed that perovskite CoTiO3 existed in all samples. Anatase p hase was also detected in samples sintered at 700 ℃ and when sintering the mixt ure at above 900 ℃, rutile phase formed with anatase phase disappearing. All sa mples exhibited room-temperature ferromagnetism (RTFM) after being hydrogenated in 10％ H2/Ar mixed atmosphere for 1 hour at 500 ℃. X-ray photoelect ron spectroscopy (XPS) showed that Co existed in the +2 formal oxidation state, and no Co clusters were detected. XRD showed that CoTiO3 disappeared and a new phase CoxTi1-xO2-δ formed after hyd rogenation. It is suggested that hydrogenation causes the phase transformation f rom CoTiO3 to CoxTi1-xO2-δ. RTFM of the sample originates from the intrinsic ferromagnetism of CoxTi1-xO2-δ. The exchange interaction between Co2+ occ urring with the phase transformation may be the essential reason for RTFM.