Harmful cyanobacterial bloom is a serious threat to global aquatic ecology and drinking water safety. Electro-Fenton (EF) has emerged as an efficient process for cyanobacteria and cyanotoxins removal, but high consumption of energy and chemicals remain a major bottleneck. This study presents a novel convertible three electrodes Electro-Coagulation-Fenton process for cyanobacteria and cyanotoxins removal with low energy consumption and no chemicals addition. We for the first time demonstrated the freely alternating between Electrocoagulation (EC) and EF by switching electrodes. The optimal aerated EC was operated at pH 8 and 100 mA to remove 91 +/- 2% of cyanobaterial cells and 15% of Microcystins (MCs). Coagulants generated in EC were adsorbed on cyanobacterial cells to form a protect layer against algae disruption and cyanotoxins releasing. Residual MCs and cyanobaterial cells were completely mineralized by EF at 28 mA with iron ions and H2O2 generated in-situ. Compare to traditional EF, the optimal Electro-Coagulation-Fenton process increased total organic carbon (TOC) removal efficiency by 30%, yet energy consumption reduced up to 92%. The novel Electro-Coagulation-Fenton process is a promising technology for the efficient treatment of the mixture of suspended solid pollutants and persistent organic pollutants in one system with low energy consumption.