Research conclusions: The loess slope can be divided into 6 types：neo—loess slope，old+neo—loess slope，old loess slope，the neo—loess+bedrock slope，the old loess+neo—loess+bedrock slope and the old loess+bedrock slope．The styles，characteristics，formation mechanism and the hazard of deformation failure of these six types of slope are analyzed，and the stability evaluation criteria for them are worked out．Through the analyses of the stability of loess slope Mong the Taiyuan—Zhongwei Railway，the control measures for the disaster of loess slope are suggested with the certain significance to the loess slope along railway line．