Optical bistability has been investigated in granular metal-dielectric composite media at high temperatures. Based on Maxwell-Garnett approximation and the spe ctralrepresentation, we calculate numerically the electric field as a function of the applied electric field E２０,and thus the opticalbistability can be studied.We show that the width of optical bistability decreases with increasing temperature.Furthermore, we study the dependence of the refractive index and the extinction coefficient on the temperature.