Local quantitaive analysis of small amounts of oxygen in titanium was studied using the secondary ion mass spectrometry (SIMS). Cs⁺ ion was used for the primary ion beam, and ¹⁶O⁻, ⁶⁴TiO⁻ and ⁹⁶Ti₂⁻ for the secondary ones. The intensity profiles of the secondary ions against energy at sputtering (energy profile) showed a good similarity between the cluster ions, i.e., TiO⁻ and Ti₂⁻. The precision of oxygen analysis was improved due to the similar energy profiles of the two analytical ions. Using the high energy resolution of mass spectrometer and the stable extraction voltage of secondary ions, the effect by mismatching in the energy profiles was reduced. The relative standard deviation of the ion intensity ratio I[⁶⁴TiO⁻]⁄I[⁹⁶TiO₂⁻] was suppressed less than 10% over the oxygen concentration of 23 to 1540 mass ppm.