The goal of this study was to determine the desired preparation conditions of polyethersulfone (PES) membrane for the microfiltration of oil-in-water emulsion. Membranes were fabricated via combination of vapor induced phase separation (VIPS) and non-solvent induced phase separation (NIPS) methods. SiO2 nanoparticle were used as the hydrophilicity modification agent in the casting solutions which led to a negative impacts on the permeate flux in high concentrations due to aggregation. The effects of nanoparticle concentration, exposure time and relative humidity on the permeate flux, and their interactions were determined. The morphology of the prepared membranes were studied using FESEM, pore size distribution, contact angle, porosity, and water uptake measurement. Besides, response surface methodology (RSM) and central composite design (CCD) were applied for modeling, statistical analysis and optimization of oil-in-water emulsion microfiltration. The most significant interactions were observed for the exposure time and relative humidity, and a contradictory trend was found for flux variation. The optimum preparation conditions for nanoparticle concentration, exposure time, and humidity were found to be 1%, 33s, and 80%, respectively, where the oil rejection was higher than 98% for all runs. (C) 2015 Elsevier B.V. All rights reserved.