The determinaiion of a timescale is necessary for estimating the rates of molecular and morphological changes in organisms and for interpreting the patterns of macroevolution and biogeography. The traditional fossils records and the new-emerging molecular clock study are two methods by which the time of origin of biologic lineages and divergence in the Precambrian can be estimated. The Precambrian, spanning the six sevenths of the Earth's life, is a period of specialimportance for the evolution of the Earth and the life on it. There have long been disputes about the time of origin of microbes that were quite prosperous in the Precambrian and the divergence time of metazoans. In summing up the fossil records and data of the molecular clock study, the authors find that the time of origin of early-stage microbes obtained by the molecular clock study is notably later than that recorded by fossils, while the estimated divergence time of the metazoans is earlier than that indicated by the fossil data. In the paper an attempt is made to interpret these major discrepancies by analysing the characteristics of the two methods.