Abstract: In order to overcome the shortcomings of the traditional stability safety factor, in this paper, the unload-load response ratio based on coupling of dynamic and displacement is used as the new stability safety factor to evaluate the stability of slope. In view of the connotation and the limitations of the traditional safety factor of slope, the use of the reliability degree to reflect the slope safety degree is proposed by using the reliability analysis method. From the damage mechanics, the parameters of the unload-load response ratio is derived through the damage variable. It is demonstrated that the unload-load response ratio as an expression of reliability can quantitatively characterize the safety degree of slope. The practical application and advantages of the unload-load response ratio are analyzed, the results further show that it is reasonable, practical and effective taking the unload-load response ratio as a new kind of safety factor of slope.