The conditions and factors which determine and affect the temporature peak in the materials during infrared heating are discussed. The temperature fields in dry materials with constant thermal properties during infrared heating are calculated bynumerical method with a transient one-dimensional combined radiative-conductive heat transfer model. The results show that the radiation is the main factor to cause the temperature peak, and the essential conditions for the existence of the temporature peak are the following: (a) there is irradiation on the surface; (b) the transmissivity of the surface is not equal to zero; (c)the material is semi-transparent; (d)the heated surface is cooled by convective heat transfor. The effects of absorption coefficient, refractive index, heat conductivity, convective heat-transfer coefficient and radiative properties of the surf ace on the temperature field are discussed too.