Transition energies, wavelengths and dipole oscillator strengths of 1s22p - 1s2nd (3 ≤ n ≤ 9) for Fe23+ ion are calculated. The fine structure splittings of 1s2nd (n ≤ 9) states for this ion are also evaluated. The higher-order relativistic contribution to the energy is estimated under a hydrogenic approximation. The quantum defect of Rydberg series 1s2nd is determined according to the quantum defect theory. The energies of any highly excited states with (n ≥ 10) for this series can be reliably predicted using these quantum defects as input. The results in this paper excellently agree with the experimental data available in the literature. Combining the quantum defect theory with the discrete oscillator strengths, the discrete oscillator strengths for the transitions from same given initial state 1s22p to highly excited 1s2nd states (n ≥ 10) and the oscillator strength density corresponding to the bound-free transitions is obtained.