The main disasters and diseases such as earthquakes,geological hazards,windblown sand,frescoes' and painted sculptures' diseases,damages caused by tourism,harmful effects of human activities etc.in the Mogao Grottoes are summarized.The factors and background causing the disasters are analyzed and the comprehensive countermeasures against diseases are put forward.The results in this paper provide a theoretical and practical basis for the scientific conservation of these grottoes and the restoration of cultural relics.