The efficiency of the hemodialysis membrane has been widely improved by blending small molecular additives and modifying the membrane surface for patients with chronic or acute kidney disease. However, a qualified sieving property, flux, and hemocompatibility are intractable to give consideration simultaneously, while the elution of small-molecular additives and modifiers easily cause coagulation, complement activation, etc. Fortunately, the BCP methoxy polyethylene glycol-polyethersulfone-block-methoxy polyethylene glycol (mPEG-b-PES-b-mPEG) based membranes exhibiting great potential for sieving in middle molecular toxin and compatibility between mPEG-b-PES-b-mPEG and PES, is nearly unfeasible elution during hemodialysis, by reason of including bounded hydrophilic segments by chemical bonds. Here, the mPEG-b-PES-b-mPEG is synthesized to fabricate the membranes, including blend membranes and BCP membrane. As a result, the blend membranes have shown an increasing flux, hemocompatibility, and sieving of lysozyme with the increasing cooperation of mPEG-b-PES-b-mPEG, the block copolymer (BCP) mPEG-b-PES-b-mPEG membrane has shown better balance than the blend membranes in flux, sieving, and hemocompatibility. Besides, for exploring further possibilities, the typical blend membrane M4 (mPEG-b-PES-b-mPEG: 20%, PES: 5%) and BCP membrane M5 (mPEG-b-PES-b-mPEG: 25%) are post tailored by ethanol at 50 °C for 2 h. This process leading the typical membranes to an efficient flux (M5-P: 442.22 L m−2 h−1) and sieving performances (M5-P: the urea and lysozyme sieving of 96.43% and 74.97%) due to the effect of ethanol at the micro-molecular chain movements and microspheres transfer. Our work presents BCP mPEG-b-PES-b-mPEG a promising future in hemodialysis membranes according to the superior performances of flux and sieving.