Abstract As the key components in a liquid desiccant dehumidification system, liquid desiccant regenerator produces great effect on the whole system’s performance. This paper studies the counter-flow ultrasonic atomization liquid desiccant regenerator. Firstly, a mathematical model for the regenerator has been established and experimentally validated with finite difference method. Two performance indicators, i.e., the moisture removal rate and the regeneration thermal efficiency, were suggested to evaluate the performance of the counter-flow regenerator, and the influences of inlet parameters on the regeneration performance of the counter-flow regenerator have been investigated by the established model in this study. Decreasing temperature difference and increasing humidity difference between air and solution can improve regeneration performance. With the temperature of air and solution increasing, the regeneration efficiency increases, but the energy loss also increases. The regeneration efficiency decreases with the increase of solution concentration. The regeneration efficiency increases nonlinearly with the increase of gas-liquid ratio. Finally, there exists an optimum droplet size for the best regeneration performance. Compared with the parallel-flow configuration, the counter-flow has better regeneration performance, which is attributed to the more uniform distribution of moisture transfer driving force and the longer residence time of droplets in the regenerator. The study contributes to the development and the better applications of the counter-flow ultrasonic atomization liquid desiccant regenerator.