Abstract: The theory of supporting arch is introduced into the study of slope deformation stability in the dump field, and the criterion of slope instability displacement is deduced, and the results are applied to the engineering example. Based on the analysis of the principle of soil arch and the existing conditions of supporting arch, a method for identifying the failure of supporting arch in the whole deformation process of dump slope is proposed. Based on the maximum deformation criterion in the deformation stability, the deformation stability coefficient is defined by the relation between the critical slip value and the real time displacement value. The displacement instability criterion is derived by supporting the peak strength point displacement of the arch. The research results are applied to the stability management of the dumping ground in the southern end of Heidaigou Open-pit Mine, which effectively ensures the safety of the personnel and equipment.