<p>High temperature industries are a critical focus for energy conservation and carbon reduction. As fundamental materials for these industries, refractories urgently require the development of high-performance, low thermal conductivity, and long service life materials to support green and low carbon development. To achieve refractories with both low thermal conductivity and excellent service performance,porous anorthite-spinel refractories were developed via in-situ decomposition pore-forming technology. The effects of spinel on microstructure evolution, strength, and thermal conductivity were investigated, supplemented by thermodynamic calculations. The results indicated that the porous anorthite-spinel refractory primarily consisted of anorthite and spinel, with minor corundum. Small-sized spinel particles were uniformly dispersed in the matrix, while the spinel reaction layers forming on the surfaces of large-sized crushed powder particles, wrapping around the remaining unreacted particles. The improvement of the degree of direct bonding between anorthite and spinel in the matrix and the small amount of diffusely distributed in situ spinel forced the deflection of the crack extension paths, which was conducive to the enhancement of the compressive strength of porous anorthite-spinel refractory. The optimized composition had 20&#xa0;wt.% spinel and its apparent porosity and cold compressive strength were 43.6% and 37.8&#xa0;MPa. Compared to porous anorthite refractories, the porous anorthite-spinel refractories exhibited a 21% reduction in thermal conductivity (500&#xa0;°C), and a 12% improvement in cold compressive strength. Valuable insights for the resource utilization of corundum dust and the design of energy efficient refractory insulation layers in high temperature industries are provided by this study.</p>