In order to meet the requirements of patients and surgeons simultaneously for spinal fixation applications, β-type Ti-Cr based alloys with self-tunable Young's modulus due to deformation have been developed to prevent the stress-shielding effect for patients and to suppress springback for surgeons. In this study, the effects of Cr and O on the deformation-induced ω phase transformation were investigated to optimize the Cr and O contents in ternary Ti-Cr-O alloys in order to achieve a large increase in Young's modulus via deformation-induced ω phase transformation with good mechanical properties. The Young's modulus of the alloys with same Cr content after solution treatment increases with increasing O content because of solid-solution strengthening effect of O. The increase in Young's modulus during cold rolling is larger for the alloys with lower O and Cr contents because larger amount of deformation-induced ω phase is formed. With regard to tensile properties, the tensile strength of the alloys subjected to solution treatment increases and the elongation of them decreases with increasing O content and decreasing Cr content because of both the effects of solid-solution strengthening of O and the deformation-induced ω phase strengthening.