Abstract: A heterotrophic WLZ-H strain growing fast was screened from natural waters. The cell morphology of the alga strain was analyzed with scanning electron microscope and, in combination with 16S rDNA molecular biology identification method, it was preliminarily conclude that the WLZ-H strain belonged to Chlorella sorokiniana.Single environmental factor test on the WLZ-H strain showed that the concentration of KNO₃ and glucose had significant effects on WLZ-H strain growth; too high temperature would decrease enzyme activity of WLZ-H strain and consequently decrease its growth; pH would change with the growth of WLZ-H strain and reach the suitable value in different growth phase.The optimal growth conditions of WLZ-H strain were:initial pH 7.0, KNO₃ content 1.5 g/L, glucose content 40 g/L, temperature 31 ℃.