All organisms regulate their life activities through the biological clock, which makes a variety of activities regular. For example, many physiological activities such as sleep-wake cycle, temperature, heart rate, blood pressure, endocrine and metabolic activity of the kidney and liver are subject to the regulation of circadian rhythms, that is to say they are all under the control of circadian pacemaker. Physiological activity of cell cultured in vitro also possess rhythms.This paper conducts a brief overview of biological clock of cell cultured in vitro and analyzes the molecular mechanism of the biological clock of the neurons and peripheral tissue cell as well as the existing problems, which provide reference for comprehensive interpretation of the molecular mechanism of biological clock.