Electrochemical processing combined with the system of microalgae Chlorella vulgaris was used to treat the synthetic organic wastewater in this paper. The effect of wastewater concentration on the biomass growth and nutrients removal was investigated. Three levels of the wastewater concentrations were ranked as "Low", "Mid" and "High", respectively. After 2 h of electrolysis pretreatment and 10 d of microalgae cultivation, TOC, NH4-N, and TP concentrations in the group "Low" were reduced by 83.7%, 99.3% and 95.0%, respectively. The Chlorella vulgaris in the groups "Mid" and "High" without electrolysis pretreatment did not survive longer than 24 h, whereas it grown well in the wastewater pretreated by electrolysis. The dry weight (DW) of Chlorella vulgaris in the group "Low" with electrolysis pretreatment was increased from 0.048 g/l to 1.087 g/l by 10 d cultivation. Results indicate that electrolysis pretreatment for wastewater can provide appropriate conditions for the subsequent biological treatment and efficiently promote the biomass growth of Chlorella vulgaris.