Abstract: For the non-caving problem of coal seam in some mines of our country, we propose a technology using liquid CO₂ phase-transforming fracture to forcing seam roof collapse. This technology uses the power of the liquid CO₂ phase transformations in working face to destroy the overlying roof and make main roof would be able to caving after the working face advancing, and ensure the normal order of the working face production. This technology is used to deal with the problem that roof does not collapse in Jiulishan Mine, and achieves desired results. The technical advantages are safe, reliable and easy to operate. Lastly, by the help of numerical simulation software COMSOL, this paper simulates the process of breaking down and proves the reliability of the technology, the obtained simulation results also fully verify the reliability of the technology.