This study investigates the effect of ultrasound on the evaporation and crystallization of sessile NaCl solution droplets in traveling and standing wave ultrasound fields. The results show that ultrasound significantly accelerates the evaporation rate and refines the crystal grains. In the traveling wave ultrasound field, the evaporation time and the time for the appearance of NaCl grains increase with the droplet-emitter distance, while in the standing wave ultrasound field, the evaporation rate increases with the droplet-emitter distance. The traveling wave ultrasound field has a stronger effect on grain refinement compared to the standing wave ultrasound field. The grain refinement is attributed to the decrease in the critical nucleation radius due to ultrasound energy and the increase in the nucleation rate due to the accelerated evaporation rate. Additionally, ultrasonic cavitation can also lead to grain refinement by breaking up the crystals. The study provides insights into the mechanisms of ultrasound-induced grain refinement and offers a reference for controlling evaporation rates and grain refinement in saline droplets.This study investigates the effect of ultrasound on the evaporation and crystallization of sessile NaCl solution droplets in traveling and standing wave ultrasound fields. The results show that ultrasound significantly accelerates the evaporation rate and refines the crystal grains. In the traveling wave ultrasound field, the evaporation time and the time for the appearance of NaCl grains increase with the droplet-emitter distance, while in the standing wave ultrasound field, the evaporation rate increases with the droplet-emitter distance. The traveling wave ultrasound field has a stronger effect on grain refinement compared to the standing wave ultrasound field. The grain refinement is attributed to the decrease in the critical nucleation radius due to ultrasound energy and the increase in the nucleation rate due to the accelerated evaporation rate. Additionally, ultrasonic cavitation can also lead to grain refinement by breaking up the crystals. The study provides insights into the mechanisms of ultrasound-induced grain refinement and offers a reference for controlling evaporation rates and grain refinement in saline droplets.