Abstract: Organic carbon is one of the major matters for accelerating the driving of nitrogen cycle, assisting in degradation of toxic nitrogen pollution in culture water as well as maintaining culture water. As one of the most widespread andabundant renewable resources cellulose can hydrolyze -1,4-glucosidic linkages in cellulose into glucose or other soluble sugar and is the organic carbon in aquaculture. The cellulase produced by Trichoderma reesei is an extracellular enzyme, which is famous for its high production, good stability and adaptability. T.reesei is the most widely studied cellulolytic fungus. The paper reviews the structure, composition and enzyme mechanism of the related cellulase in T.reesei, introduces researches on its reconstruction of artificial breeding and genetic engineering,so as toput forward the prospects of its application in industries of food, textile, feed, agriculture and so on.