A microscopic dynamic model for particle agglomeration was developed with simultaneous consideration of multiple particle interaction mechanisms as well as mechanisms of agglomeration or rebound upon inter-particle collision. The microscopic behaviors of acoustic agglomeration of a large-sized additional particle and its two neighboring submicron-sized fine particles were numerically investigated. The results show that the major acoustic agglomeration behaviors of the bimodal particles are characterized by the agglomeration between the additional particle and either fine particle and the successive agglomerate between the addition particle and the closer and farther fine particles. The gravitational effect and acoustic wake effect play an important role in the acoustic agglomeration of bimodal particles. When the distance between the initial position of the additional particle and wave node increases, small variation in the average agglomeration time between the additional particle and the closer fine particle is observed, whereas the average agglomeration time between the agglomerate formed by the said particles and the farther fine particle decreases obviously. When the additional particle is initially close to the wave node, it is possible for the particle to agglomerate with its closer fine particle. Concerning the agglomeration between the additional particle and its closer fine particle as well as the agglomerate formed by the said particles and the farther fine particle, the average agglomeration time increases while the agglomeration probability increases first and then tends to a constant value with the increasing additional particle diameter.