In this work, in order to investigate the behavior of non-dilute drops, including breakup, coalescence and trajectory, in a 100-mm inner-diameter horizontal swirling flow field with low inlet mixture velocity, both an experimental study and numerical simulation were conducted. Inlet oil phase concentration was under 3.0% volume fraction, with an inlet flow rate ranging from 12 m(3)/h to 18 m(3)/h. Malvern RTsizer and Electrical Resistance Tomography were applied for measuring the drop size distribution and oil phase concentration, respectively. Correspondingly, numerical simulations applying a Renormalization-group k-epsilon turbulent model, coupled with a Discrete Phase Model simulating oil phase, were conducted as well. The results showed that small drops in the flow field tended to coalescence, while the behavior of large drops was determined by the inlet flow rate. A higher inlet flow rate led to a thinner oil core with constant inlet oil concentration. Moreover, the simulation results, which corresponded well with the experimental observations, presented oil drops distribution laws of breakup, coalescence and trajectory in a 100-mm inner diameter swirling flow field and established a prediction model in a similar flow field. Finally, regularity of swirling intense distribution and drop-turbulence interaction in a swirling flow field with a low inlet velocity was established. These results provide new information helpful for the design of vane-type separator. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.