Agglomeration of fine solid particles under the excitation of external acoustic field has potential applications in the field of ultra-low emission of combustion pollutants. It is expected that the performance of particle agglomeration can be improved by adding large sized liquid droplets. According to the dynamic process of acoustic agglomeration, including the particle motion, collision, agglomeration and rebound, a model of acoustic agglomeration for gas-liquid-solid three phase system with coexistence of liquid droplets and solid particles in gas phase is developed by using the direct simulation Monte Carlo (DSMC) method. Using this model, numerical simulations are performed to investigate the process and performance of acoustic agglomeration of fine solid particles under the effect of additional droplets. The numerical results are compared with experimental data, and the proposed model is validated. On this basis, the dynamic behaviors of acoustic agglomeration of fine particles in the case with additional droplets are explored. Furthermore, the influences of the diameter and number concentration of additional droplets on the performance of acoustic agglomeration of fine particles are examined. The results show that rapid agglomeration among the solid fine particles and additional droplets can be achieved by adding droplets into the acoustic field, yielding large sized liquid-solid mixed-phase particles. In this process, the agglomeration efficiency of fine particles increases significantly. It is also found that the diameter and number concentration of additional droplets are important factors that affect the acoustic agglomeration of fine particles. The agglomeration efficiency of fine particles rises, while the magnitude of increase tends to decrease with the droplet diameter and number concentration increasing. The research results can provide both theoretical basis for modeling the agglomeration process of complex particle systems and method guidance for achieving the ultra-low emission of fine particles from combustion sources.