Abstract This review was written on the basis of some major books about the circadian rhythm and many papers published recently. It is introduced as follows:I .The early history and development of the circadian rhythm researchThe astronomer,De Mairan (1729) was the first to make an experiment showing that plant leaves periodically move in constant darkness and temperature.De Candlle(1832) clearly realized that leaves movements were caused by inherent diurnal rhythm, later on,the inhertance of the mammlian diurnal rhythm was further verified by Aschoff in 1955.Aschoff(1954) introduced the term "zeitgeber" and considered that light is a most important one.Before long, the circadian temperature indenpend-ence was proved by Rawson in 1956 and Sweeny et al. in 1960. Nieborj (1958) observed the circadian change of the cell nucleus size in rats.Halb-erg(1953) had a remarkable discussion that DNA and RNA both play a part in circadian rhythm.Application of feedback theory, black-box analysis as well as theory of oscilator and serve mechanism pushed the biolgical research a great forward. It was reported that biochmical feedback system may serve as the mechanism of biological clock. Establishment of models was currently ava- ilable in 1960's and a great number of models have been emerged.An important models were coupled oscilltor model of Pittendrigh et al.in 1957 and Wever model of Wever et al. in 1965.Ⅱ . Present situation and trendsLocation of biological clock remained elusively for long time. Many authors, Hedlud,(1977); Hoffmann, (1981)and Illnerova et al. (1984) have showed successfully a "pineal clock" and proposed that pineal gland serve as an important intermediary in the synchronization of mammalian circadian rhythm. Moor (1980) did great achievements concerning pacemaker of the circadian rhythms.More and more researchers paid much attention to what's going on in biological rhythm at the biochemical and molecular levels.Such as Chance's feedback loop model in 1967, Watson's tape-reading trascription model in 1970 and Njus's membrane model in 1974, which made some suggestions in clock mechanism.Macroscopic work mostly denotes some ecological researches, such as, "seasonal rule",oxygen consumption rhythm, functional taxonomy, etc. It is worth wiling that Aschoff(1964) offered the Aschoff Seasonal Rule which seems successful in practical applications.In China circadian rhythm research rose from 1970's. Circadian locom-otor rhythm in pikas, voles, zokors, and tree shrews were recorded, and oxygen consumption rhythm have been studied in pikas and zokors.In mic-rocosmic area, circadian rhythm of the corticosterone level and the electroencephalogram of sleep and wakefulness have been documented in pikas, rats and tree shrews.