Abstract: The thermal elastic plastic model and finite element software were used to simulation the whole process of underground coal gasification, and obtained displacement of different positions of roof rock, then contrasted to the traditional coal mining. The results showed that:in the processing of underground coal gasification and coal mining, the roof strata movement curve consistent with a negative exponential functions the sinking speed of coal gasification roof is faster than the sinking speed of coal mining, and vertical displacement is larger; the nearer from the roof, the greater of the vertical displacement, especially the direct roof displacement increases rapidly.