This study was performed to investigate the availability of forward osmosis (FO) for microalgae harvesting using sulfonated polyethersulfone (SPES)/PES porous membranes. In FO process, porous membranes (< 25.0 L m −2 h −1) exhibited more superior water flux than TFC FO membranes (<2.6 L m −2 h −1). Furthermore, the incorporation of SPES has been demonstrated to enhance membrane performance. The effects of SPES content on pore structure and separation performance were investigated. Compared with pure PES porous membranes, porous membranes with 40% SPES yielded an improved hydrophilicity and greater porosity. It exhibited two times higher water fluxes than the pure PES porous membrane. For microalgae harvesting, AL-FS mode (active layer facing the feed solution) was more favourable than AL-DS mode (active layer facing the draw solution) because less deposited microalgae on the active layer mitigate the membrane biofouling. FO operation combined with SPES/PES porous membranes is conducive to preserving microalgae cell integrity under the mild condition. In addition, FO membrane can be cleaned by a simple water rinse. Potential implications were highlighted as a sustainable method for microalgae harvesting because of no pressure input and less chemical cleaning demand.