In this paper, the hydrodynamic behaviour of oil field wastewater treated by ultrafiltration process was studied. The results were obtained as: under certain operation parameters, the rejection coefficients of both oil/water and turbidity are maintained over 0.96 and 0.97, respectively; while, temperature has no obvious effect on the rejection coefficient of oil/water and turbidity. Moreover, the tangential velocity has a positive effect on maintaining a relative high permeate flux, and this effect is even more obvious at higher trans-membrane pressures; meanwhile, the rejection coefficients improved with tangential velocity increasing until 0.4 m/s, once the velocity goes beyond this value, the rejection coefficient decreased. (C) 2012 Elsevier B.V. All rights reserved.