A polarizing microscope, X-ray diffraction (XRD), fourier transform infrared spectrometer (FTIR), scanning electron microscope and energy dispersive spectrometer (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and micro computed tomography (Micro CT) were used to investigate the relation between the structure and properties of the composite. Meanwhile, the physical properties, mechanical properties and strength mechanism were researched. The experimental results show that the structure and morphology of coated phosphogypsum remain intact in the composite, which shows good compatibility and forms a clear interface layer of transition zone between the coated phosphogypsum and the matrix, conforming to the structure of particle reinforced inorganic composites. The emulsion coated phosphogypsum has a certain strengthening effect on the aluminous rock mineral polymer composite. The compressive strength of the composite can reach 16.5 MPa when the amount of coated phosphogypsum is 40%, and the apparent density is 1.75 g·cm-3, which is significantly lower than that of common concrete; the thermal stability of the composite is also improved to a certain extent. Some certain chemical reactions occur in the process of forming the matrix of aluminous rock mineral polymer materials, with a structure of three-dimensional network. The research will provide a new way for the comprehensive utilization of phosphogypsum and low-grade aluminous rock.