Abstract: The multi-block upper bound method is a good choice for the stability analysis problems in the geotechnical engineering. It is simple, highly effective and of rigorous theoretical basis. According to the usage process of the multi-block upper bound method, some simplifications are made for the basal stability analysis of braced cuts in clay. After the simplifications, a new method based on the upper bound method is proposed for the basal stability analysis, and the detailed calculation process is discussed. Considering different soil strength indices used in practice, the calculation methods for consolidated-undrained strength and unconsolidated-undrained strength are put forward respectively, and they can be used in practice at home and abroad. Several calculations are presented to analyze the effects of some important factors on the basal stability safety. Finally, a real excavation case is calculated and comparisons are made with the methods recommended in the codes to examine the proposed method.