Standard sequences involve HST, TST, FSST and LST. Through analyzing the features of onlap points in the systems of standard third-order sequences, the onlap points of a standard sequence can be divided into five kinds, which are onlap points of LST, onlap points of TST, onlap points of early HST, onlap points of late HST and onlap points of FSST. And bring forward the way of inverting lake level change history by counting onlap points in the sequence. Use this method, the authors find that the lake level is highly confident curve, it also proves that the way of inverting lake level change by counting onlap points is practicable in the study of continental paleolimnology.