Because of the effect of silicon on the formation of oxide scale,red scale is the main surface defect of hotrolled Fe-Si plate,making the scale difficult for descaling compared with carbon steel.Thermogravimetric analyzer(TGA)is used to simulate isothermal oxidation process of Fe-1.5Si alloy for 60min under air condition,and the temperature range is from 700to 1 200℃.Electron probe microanalysis(EPMA)is used to observe cross-sectional scale morphology and analyze elemental distribution of the scale.Relational graph of temperature,scale thickness and scale structure is obtained.It is found that scale structure(outer Fe oxide layer+inner FeO/Fe2SiO4layer+internal Si oxide precipitates)is almost unchanged with temperature except at 1 000and 1 200℃.At 1 000℃internal Si oxide precipitates cannot be found at the subsurface of the alloy,and at 1 200℃FeO/Fe2SiO4not only forms a layer as usual but also penetrates into the outer Fe oxide layer deeply. Because of the effect of silicon on the formation of oxide scale, red scale is the main surface defect of hotrolled Fe-Si plate, making the scale difficult for descaling compared with carbon steel.Thermogravimetric analyzer (TGA) is used to simulate isothermal oxidation process of Fe-1.5Si alloy for 60min under air condition, and the temperature range is from 700to 1 200 ° C. Electron probe microanalysis (EPMA) is used to observe cross-sectional scale morphology and analyze elemental distribution of the scale. , scale thickness and scale structure is obtained. It is found that scale structure (outer Fe oxide layer + inner FeO / Fe2SiO4layer + internal Si oxide precipitates) is almost unchanged with temperature except at 1 000 and 1 200 ° C. At 1 000 ° C internal Si oxide precipitates can not be found at the subsurface of the alloy, and at 1 200 ° C FeO / Fe2SiO4not only forms a layer as usual but also penetrates into the outer Fe oxide layer deeply.