The invention relates to a light thermal-shield refractory castable comprising the following components in percentage by weight: 40-60% of light aggregate, 10-20% of capacitance mullite, 5-10% of kyanite powder, 5-10% of high-aluminium clinker powder, 3-8% of silica micro powder, 3-8% of alpha-Al2O3 micro powder, 5-10% of high-aluminium cement, 0.5-10% of high-aluminium refractory fibre containing zirconium, 1.5-4% of thermal-shield steel fibre, 0.1-1% of melamine and 0.05-0.1% of organic anti-explosion fibre, wherein the granularity of the capacitance mullite is less than or equal to 1 mm, both the granularity of the silica micro powder and the granularity of the alpha-Al2O3 micro powder are less than or equal to 5 mu m, and the chemical modified light aggregate is obtained by drying after the light aggregate is dipped in inorganic chemical solution or sol. The light thermal-shield refractory castable of the invention can improve the service life of a furnace roller, lowers production consumption cost, reduces non-working hours caused by exchanging rollers and improves production efficiency.