In this talk, I would like to introduce the effects of disorder on three topological insulator (TI) systems. In the one-dimensional model, it is shown that disorder drives topological phase transitions between different topological indices. The mechanism is explained by band gap renormalization and Anderson localization, as a consequence of disorder scattering.  The second system is a TI nanowire threaded by magnetic flux. The theoretical results based on the Landauer-Buttikerformalism show that Aharonov–Bohm oscillation appears in the disordered limit. By analyzing the localization length, it is shown that the bulk states are localized by disorder scattering and fail to contribute to transport. Lastly, in the presence of a rotating magnetic field, a reentrant quantum spin Hall effect is predicted. The numerical simulation shows that the reentrant quantum spin Hall effect survives the disorder strength up to eight times the energy gap, confirming its robustness.