Abstract: In order to study the factors to cause the roof disasters and the prevention and control method, based on the roof disaster causes, the roof disasters of t he fully-mechanized coal mining face could be divided into the roof flling at the coal wall of the coal mining face, the roof falling at the exit of the coal mining face, local roof falling in the geological structure region, the collapsed type roof falling under the complex roof, the collapsed type roof falling and large area roof falling.The roof disasters of the mine gateway could be dividedin to the roof flling of the gateway driving face, the roof flling at the crossing point of the gateway and the roof fling of the gateway in the structure region. The summarization showed that the factors to cause each kind roof disaster would mainly be the seam inclination, the properties of surrounding rock, the geological structure and other natural factors and the mining method, roof control, gateway layout and mining technical factors.The prevention an d control idea of the roof disaster was provided with the object understanding, optimized design, monitoring and measuring early warning and timely control.The KJ21 m ode roof disaster monitoring and measuring system was applied to the real time monitoring and measuring and the early warning of the roof.The measures to timely spe ed up the pushing forward speed of the coal mining face and to improve initial support force of the powered support could effectively protect the roof safety of the coal mining face.