The effect of different length and concentration of basalt fibers have been studied in this research which effects the thermal properties of intumescent coating. The investigated intumescent coating formulations, containing ammonium polyphosphate (APP), melamine (MEL), boric acid (BA), expandable graphite (EG), epoxy resin (NPEL-128) and polyamide amine hardener (H-2310) were reinforced with 0-1 wt. of basalt fibers of each 6 mm and 12 mm. The effects of the basalt fiber�s length on the char expansion and thermal stability of the intumescent coating, as well as on the char morphology and composition were studied. The char expansion was analyzed using a Carbolite furnace. Field emission scanning electron microscopy (FESEM) and Thermal stability test were carried out using thermogravimetric analysis (TGA). Furthermore, the morphological study confirmed that long fibers (12 mm) of basalt fibers form a network which protects the underlying steel substrate at elevated temperature in the event of fire. Elemental analysis showed that ICF-B1-12 has enhanced carbon content of 63.1 in the residual char. Thermogravimetric analysis results showed that BF reinforced formulations; ICF-B1-12 has 34 of residual weight at 800oC which is more thermally stable among all formulations. © BEIESP.