Abstract: In order to research roof control effect of two-legs shield support in ultra large fully mechanized caving face, the paper theoretically analysed roof control mechanism of two-legs support, established the numerical model of two-legs and four-legs shield support that front column angle were 85°and 90°, contrastive analysed the roof control effect of different types support to fully-mechanized caving coal face. The results showed that mechanical model of top-coal was nonsymmetrical caving arch model result in the wall side and support side of roof coal in different horizontal load, and horizontal force pointed to the direction of the wall side was conducived t 0 top coal stability.The stabilization of both two-legs and four-legs shield support were not good under the front column angle was 90° .The stabilization of two-legs shiel d support was better than the four-legs shield support under the front column angle was 85° reslut in two-legs shield support produced greater horizontal force pointed t 0 the direction of the wall side.