The Fe0.7 Co0.3 - SiO2 granular alloy solid has been prepared using a sol-gel method, and investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The effective magnetic anisotropy KE has been measured by the law of approach to saturation (LATS). The evolution of the magnetic properties for the granular alloy solid during reducing is described and explained by means of particle size distribution and superparamagnetic behaviour. When the measuring temperature changes from 100 to 800 K, the variations of saturation magnetization, effective magnetic anisotropy and coercivity of the Fe0.7 Co0.3-SiO2 granular solid are much smaller than those of existing magnetic recording media. The Fe0.7 Co0.3 - SiO2 granular alloy solid has a potential for application in high density magnetic recording media, which can be used in a wide temperature range.