<p>The stability analysis of dangerous rock mass is the key to preventing and controlling dangerous rock mass collapse as a geological disaster. Indeed, it is of great practical significance to propose a scientific and relatively accurate stability computation method for predicting the collapse of dangerous rock mass. Based on conventional limit equilibrium, this study proposes a new theory considering the size effect of dangerous rock mass under various blasting vibration loads to assess its stability. The approach considers dangerous rock mass shape, geometrical size, blasting vibration frequency, and the initial phase of the blasting vibration wave in different directions. Based on the slice method, it establishes the stability analysis and calculation of dangerous rock mass, considering the size effect under blasting vibration. The corresponding calculation program is compiled using MATLAB to carry out calculation examples. The results indicate that the calculated minimum stability coefficients of dangerous rock mass in this study are proximate to those calculated by conventional pseudo-static analysis. However, this study's calculations are slightly larger than those computed by pseudo-static analysis, with a relative difference between 5.1% and 8.2%. The method proposed in this study provides a reference for dynamic stability analysis and evaluation for dangerous rock mass.</p>