To improve low-efficiency and durability for alkaline membrane water electrolysis, novel piperidinium functionalized SEBS (SEBS-Pi) alkali membrane was prepared. The membrane not only displayed high conductivity ( > 10 mS cm(-1) at 30 degrees C), but possessed excellent thermal stability and mechanical properties. Alkali resistance test lasts 576 h in 1 M KOH at 80 degrees C, high retentions of IEC as well as conductivity and no obvious change in FTIR spectra suggest good alkaline resistance of SEBS-Pi membrane. Good three phase reaction boundary in catalyst layers and packing between the membrane and catalyst layers are formed when SEBS-Pi is used as both membrane and ionomer. A good performance of water electrolysis is achieved (400 mA cm(-2) at 2 V, 50 degrees C). During a long-term electrochemical stability test carried out with current density of 400 mA cm(-2) at 50 degrees C for 105 h, the voltage remained almost constant (around 2.08 V), indicating good cell durability. All these indicate that SEBS-Pi has a good potential for applications in water electrolysis.