In this study, RuO2-embedded PES membrane was prepared and it was used for protein separation. The antifouling properties of the fabricated composite membranes were also investigated using bovine serum albumin (BSA) as protein solution. The mean roughness increased proportionally by introducing RuO2 particles. The porosity of the composite membranes was higher than that of the pristine PES membrane. On the other hand, composite membranes has smaller average pore size after addition of RuO2 particles. The blending of RuO2 particles to the PES membrane caused to increase the hydrophilicity of the pristine membrane from 76.67° to 67.13°. The thermal studies of the PES/RuO2 membranes were performed by DTA/TG. The Activation Energy (Ea) values of the PES/RuO2 membranes were found to be 57.67-641.34 kJ/mol for Flynn-Wall-Ozawa (FWO) and 55.13–659.10 kJ/mol for Kissenger-Akahira-Sunose (KAS). The pure water flux of the composite membranes decreased from the pristine PES to PES/RuO2 1.00 wt%. The pore size was calculated as 14.5 nm and pore size decreased up to 6.5 nm when blended RuO2 particles increased up to 1.00 wt.%. BSA fluxes were 84.1 ± 2.1, 86.3 ± 2.5, and 93.9 ± 3.2 L/m2/h for pristine, PES/RuO2 0.50 wt%, and PES/RuO2 0.75 wt% membranes, respectively. PES/RuO2 1.00 wt%. membrane supplied the lowest BSA flux (73.6 ± 3.1 L/m2/h). BSA rejection efficiencies increased from 45.5 ± 1.8% to 92.6 ± 1.5% when blended RuO2 particles increased from 0 to 1.00 wt%. The results depicted that Rir values decreased while Rr values increased after the blending of RuO2.