In recent years, endophytes such as endophytic bacteria, endophytic actinomycetes and endophytic fungi have become the popular topics in biology. In this article we started with comparing different definitions of endophytes, proposed broad and narrow conceptions of the organisms, then summed up their species diversity, distribution and their physiological metabolism characters, analyzed the relationship between endophytes and host plants, and discussed endophyte potential values and its application prospects in order to provide ideas and bases for promoting endophyte study.