Chitinases, hydrolyzing specifically β-1,4 glucosidic band of chitin, play an important role in carbon cycle of nature, and have a wide distribution and a variety of functions. Chitnases are invovled in the growth, development of fungi and have a key role in plant protection against fungal pathogens. The present situation and the latest progress in chitinase research are reviewed, including the distributions, physical, chemical and catalytic properties, localization in cells and regulation of chitinases, and the latest progress in fungi and plant chitinases research are summerized briefly.