Docosahexaenic acid production by Schizochytrium sp.using molasses as carbon source was studied: Molasses from different sugar refineries were prepared as carbon source. Molasses sources and molasses proportion in the medium were investigated to evaluate the effect on the resultant dry cell weight, total lipid content and DHA yield. The results indicated that the colloid and excessive metal ions in the cane molasses had the noticeable negative effects on the Schizochytrium sp.growth, the result was depressing even if the proportion of molasses significantly reduced.The application of the cane molasses as a substitute carbon source in the actual production was limited.On this basis the prospect of refined sugar molasses was evaluated.The result was very close between glucose and refined sugar molasses when the refined sugar molasses proportion in the medium is below 80%, refined sugar molasses may partly substitute for glucose as carbon source of Schizochytrium sp.