Bi0.5Na0.5TiO3 (BNT) is a lead-free piezoelectric material with A-site complex perovskite structure. It exhibits high Curie temperature, large electric field induced strain, special relaxor properties and large thickness mode electromechanical coupling factors. Specifically, it shows stable mechanical quality factor with the variance of temperature and vibration velocity in comparison with Pb(Zr,Ti)O3 (PZT). Thus, BNT based ceramics are expected to be applied in actuators, filters, ultrasonic transducers and other fields. However, they still have some problems, for example, low depolarization temperature (Td) making the operational temperature range of devices narrow, which limits the practical application of BNT-based materials. Therefore, the research of lead-free piezoelectric ceramics with high Td has great prospects in future. This article has reviewed depolarization behavior of BNT-based ceramic materials and three methods of increasing Td: elemental doping, composites with the second phase and quenching heat treatment, introduced the latest research progress of these methods and their mechanisms, and finally put forward several problems to be solved urgently. This review may provide a reference for further improvement of Td of BNT and other lead-free piezoelectric ceramics.