The Hirudinea in China were reviewed. The ecological distribution, population dynamic of the H.huinana, the adaptation of H. hainana to temperatures, soil humidity and pH, responses of H.hainan to temperatures, relative humidity and light, and the effects of human activities on H.hainan populations are discussed. The land leech′s behavior ecology, including locomotion of H. hainana, such as shortening, oscillating, rotating, sucker cleaning, rubbing, foraging behaviors and the factors influencing these behavior and ecological significance are also discussed. The ecology of the freshwater leeches including behaviour in paddy-fields of Ninghsien, Zhejiang province, relationship between population dynamics of Whitmania laevis and chemical factors in paddy fields of Guangzhou, chemical environment of suck-blood Hirudinaria manillensis in paddy field of Guangzhou are described. The study also discussed the foraging, growth dynamics, life recycle and reproduction biology of suck-blooding land-leech H. hainana and fresh-water leech Hirudinaria manillensis, the taxonomy, and zoogeography aspects. In addition, the morphology including histology and the anatomy of organic system of H.hainana are described. The Hirudinea can be classified into 2 subclasses, Branchiobdellidea and Euhirudinea, 3 orders Branchobdelidaida, Rhynchobdellida, Arhynchobdellida, 9 family, 33 genus and 111species The leeches responses to pesticides, including toxicity (LD50, LD95) of different pesticides to H. hainana are presented. Medical usage of the leech, Hirudins from salivary glands is anticoagulant material is discussed. Hirudin (from Hirudo medicinalis), Haemadin(from land-leech), and hementi(from Hementeria ghilianii) have been identified and isolation procedures resented.