Abstract: The article summarized the discovery,polymorphyism and important function of the timeless gene.It is one of the two firstly discovered biological clock genes.The circadian rhythms are controlled through autoregulatory feedback loop by the products of the biological clock genes including PER,TIM,CLOCK and CYCLES.The TIM may be regulated by light and form a allodimmer with PER,and the allodimmer can drive the circadian behavioral processes of Drosophila.The lucubrating of the mechanism of biological clock genes will greatly be helpful to explain the human complex behaviors.