Classical orthokinetic mechanism assumes that the fine particles near the core particle move straightly until hitting the core particle.Actually，airflow detours the core particles and the trajectories of fine particles will be deflected from straight lines by the airflow.The collision efficiency was introduced to denote the proportion of fine particles that collide with core particles.By modeling the collision efficiency of acoustic agglomeration，the effect on acoustic agglomeration was studied.The results showed that collision efficiency was very low for PM2.5 especially for PM1，which meant that the fine particles were hardly collected by orthokinetic agglomeration.Collision efficiency decreased as acoustic frequency increased，but it enlarged the range of optimum frequency of agglomeration.Higher sound pressure level（SPL）favored both collision efficiency and agglomeration kernel，so acoustic agglomeration increased in the higher-intensity acoustic field.Acoustic agglomeration was ineffective for SPL less than 140 dB.Temperature produced little influence on orthokinetic agglomeration at a low temperature，but a high temperature reduced both collision efficiency and agglomeration rate.