Cyclic sequence is a set of sedimentary formations with genetic relationship that are deposited in a cycle from prograding to retrograding

controlled by astronomical periods and bounded by maximum flooding surfaces.It records faithfully the shifting of astronomical periods.The article takes the Yanchang Formation in Well Sh99 from Ordos Basin for an example

discusses the signal decomposition and reconstruction of GR curve by using filtering DWT as well as spectrum analysis technique.The correspondent sedimentary cycle of each astronomical cycle is identified based on the relationship between master frequency ratios and astronomical frequency ratios.The cyclic sequences of the Yanchang Formation are identified with the Absdolute geologic age as constraints.The research shows that the division of cyclic sequence can be carried out reasonably and effectively with discrete wavelet transformation and spectrum analysis technique on the ground of the astronomical cycles.