<p>Nickel-based single-crystal superalloys play a crucial role in aerospace, energy, and advanced manufacturing due to their excellent high-temperature strength and corrosion resistance. Additive manufacturing can control the thermal cycle and processing capacity to process single-crystal alloys with few or no cracks. Therefore, this study summarizes the progress on the growth, stray grain formation mechanism, crack control, mechanical properties, and electrochemical corrosion properties of nickel-based single-crystal superalloys by different additive manufacturing processes and heat-treatment optimization in recent years. Under the premise of providing sufficient energy and scanning rate, appropriate heat-treatment processes are the key factors for the preparation of single-crystal structures. By precisely controlling solution temperature, aging duration, and cooling rate, γ/γ′ eutectics can be eliminated, γ′ precipitates refined, and residual stresses relieved, resulting in notable enhancements in creep strength, fatigue life, and thermal stability. Moreover, the regulation of γ′ morphology serves as a key factor governing corrosion behavior, as a uniform and finely dispersed γ′ distribution improves electrochemical corrosion resistance through the reduction of potential differences and the stabilization of passive films. In addition, appropriate management of the heat-affected zone and cooling rate effectively suppresses recrystallization and stray grain formation, maintaining single-crystal orientation and ensuring superior mechanical reliability.</p>