Endophytic fungi are a class of fungi living in the healthy plant’s tissue, or within a certain stage of its life cycle, without causing any apparent symptoms. As endophytic fungi living in the host plants of this particular micro-environment timelessly, they have formed a co-evolutionary relationship with their host plants. On the one hand, the host plants provide essential nutrients and the survival environment for endophytic fungi; on the other hand, endophytic fungi in-fluence their host plants through their metabolites, or by means of signal transduction. Meanwhile researches have shown that endophytic fungi are widely spreaded in plants and produce the same or similar biologically active components.