Organic and inorganic composite silicate thermally conductive insulating coatings were prepared by using high modulus potassium silicate solution as a base material,alumina as a thermally conductive insulating filler,and silica-propylene emulsion and defoamer. The heat conduction behavior of insulating silicate coatings was studied by testing the thermal conductivity,volume resistivity,porosity,pore size distribution and elemental distribution changes of silicate coatings. The results show that the thermal conductivity of silicate insulating coatings is enhanced by appropriately increasing the mass fraction of alumina. The spherical morphology and large particle size of alumina filler are more favourable for the improvement of thermal conductivity of silicate insulating coatings. When the filler is spherical alumina with particle size of 2.9 μm and its mass fraction is 37.5%,the thermal conductivity of coating is up to 1.072 W/(m·K),the volume resistivity is more than 108 Ω·m,and the thermal conductivity and insulating performance of coating reaches the best.