The Yanshan Movement was originally defined by Weng Wenhao. This was based on the book of “Geology of Western Hills of Peking”. In fact, there was no phasing for the Yanshan movement in that time. After the field geological investigation of Western Liaoning province, Weng Wenhao divided the Yanshan Movement into two phases, named Phase A and B. While, Phase A is the period of triggering, Phase B is the main stage. However, after the detailed literature studies, we found the inconsistency of the original definition of the Yanshan movement between Western hills of Beijing and West Liaoning province. Using comparative analysis, this paper considers that the unconformity of the Yanshan movement should be between the Yaopo coalbearing strata and the Longmen conglomerate in western hills. As well as, in the western Liaoning province, it should be between the Beipiao coalbearing strata and the Haifanggou conglomerate. In addition, this paper considers that the period A may be related to the regional major faults showing the NE extension in Chinese continent. It is most important that this paper considers the Phase A of Yanshan Movement is a very short period. Maybe, it is a starting point which constitutes the boundary point of the Phase B.