Nuclear excitation by electron capture (NEEC) in \(^{229}\) Th offers a potentially controllable route for manipulating nuclear-state populations. In this study, a systematic NEEC analysis is carried out for \(^{229}\text {Th}^{q+}\) over the charge-state range \(q=1^+\) – \(90^+\) , explicitly resolving the roles of the electronic quantum numbers (n, l, j) and of the key observables resonance energy \(E_\text {r}\) , peak cross section \(\sigma \) , resonance strength S, and total resonance width \(\Gamma _{\text {NEEC}}\) . Particular attention is paid to charge-state control of the isomeric state (IS, 8.36 eV) and the second-excited state (SE, 29.19 keV). The calculations reveal pronounced charge-state-dependent behavior. For the IS, the valid capture channels migrate toward higher n with increasing q, and the dominant principal quantum number follows \(n \approx 1.241q + 3.178\) within the present model; meanwhile, Coulomb-enhanced electron–nucleus coupling partly compensates for the loss of available channels, keeping the total resonance strength nearly charge-state independent. For the SE, the excitation energy exceeds the binding energies of almost all relevant orbitals, so channel screening is weak and the total resonance strength increases monotonically with q. These results clarify how the ionic charge-state reshapes NEEC in \(^{229}\text {Th}^{q+}\) and provide a quantitative reference for future experiments, especially those aiming to populate the IS indirectly through the SE.
