This paper reports the fabrication and filtration characterization of advanced fibrous cellulose acetate (CA) membranes for high-flux water filtration. The ultrathin nonwoven fibrous CA membranes with varying fiber diameter and areal weight were produced by electrospinning and post-processed by hot-press. The filtration efficiency of the ultrathin fibrous CA membranes was characterized by controlled water-filtration tests based on artificial colloids prepared via dispersing polystyrene (PS) particles of the diameters of 5 pin, 2 pin, 500 nm, and 100 nm in water, respectively. Natural river water was further used for evaluating the filtration capability of the electrospun fibrous CA membranes. Experimental results show that the rejection rate of the present fibrous CA membranes to PS particles with the diameter of 2 pin was up to 99.8%. In addition, the filtration efficiency of the electrospun fibrous CA membranes increased with increasing areal weight of the membranes. In the case of the filtering electrospun fibrous CA membranes with the fiber diameter of 800 nm and membrane areal weight similar to 0.005 g/cm(2), the measured turbidity of natural river water after filtration can reach as low as 0.135 nephelometric turbidity unit (NTU) while the initial flow flux can reach up to 20,455 L/m(2) hat the feed pressure 14 psi. The study suggests that low-cost electrospun fibrous membranes can be used for stable, high-flux water microfiltration with the filtration efficiency. (C) 2016 Elsevier B.V. All rights reserved.