Considering sub-micron potassium titanate whiskers (BX-101), nanoscale potassium titanate whiskers (AX-301), sub-micron potassium titanate whiskers (AX-316) and high strength potassium titanate crystal (AX-319) as functional fillers, heat resistant ablative coated fabrics which have high radiant heat reflectivity were prepared. The effect of the type of functional filler on the thermal protection performance of heat resistant ablative coated fabrics was mainly discussed. Research showed that the microstructure of potassium titanate functional filler had a significant impact on the radiant heat reflectivity and thermal insulation performance of the prepared coated fabric. The coated fabric which took nanoscale potassium titanate whiskers (AX-301) with a minimum diameter and greater length-diameter ratio as functional filler has the highest thermal reflectivity and the best insulation property. Heat ray reflectivity of potassium titanate coated fabrics had positive correlation with their crystallinities. The higher the coated fabric crystallinity was, the greater the heat ray reflectivity. Thermogravimetric analysis results showed that after adding four kinds of potassium titanate fillers, the thermal stability of the prepared coated fabrics was enhanced, and the nanoscale potassium titanate whiskers (AX-301) coated fabrics had the best thermal stability.