This paper deals with the process of preparing cast stones directly from thermal phosphorous slag liquid. In the experiment, 75% solid phosphorous slag was remelted into thermal liquid, then mixed with 25% secondary raw materials, and subsequently melted together into the modified slag liquid that was cast, crystallized and annealed, thus resulting in the formation of cast stones. XRD and SEM observations confirmed that the main crystal phase of the cast stones was β-wollastonite, and the fibriform crystals assumed compactly granular form with the size of 0.2～ 0.5 μ-m. The bending strength, alkali resistance and acid resistance of the cast stone were respectively 37.17 MPa, 0.02% and 0.42%, conistent with the quality standards of construction materials. The process presented by the authors is suitable for industrial application, and the study is also a basic work of the resource recycle of thermal phosphorous slag liquid and the environment protection of phosphor industry.