Wastewater from some chemical plant is of high content ,chroma and acid. On the base of these characters, "micro electrochemical reduction coagulation" process was opted to pretreat it and better efficiency was obtained. Running results indicated that the removal rates of COD and chroma were above 70% and 80% respectively on the best influent condition of pH=6,iron:carbon=2:3,the input rate=60% and micro electrochemical reduction coagulation was used as 1.5%.