In this study, an efficient electro-flocculation process for Dunaliella salina with energy production by aluminum-air battery has been successfully applied. The formed aluminum hydroxide hydrates during discharging of battery were positively charged, which have a great potential for microalgae flocculation. The precipitation of aluminum hydroxide hydrates by algae also could improve the performance of aluminum-air battery. The harvesting efficiency could reach 97% in 20 mins with energy production of 0.11 kWh/ kg. This discharging electro-flocculation (DEF) technology provides a new energy producing process to effectively harvest microalgae. (C) 2017 Elsevier Ltd. All rights reserved.