Ti O 2 -based magnetic semiconductors with high Co doping concentrations (Ti1−xCoxO2) were synthesized under thermal nonequilibrium condition by sputtering machine. Microstructure and composition analysis by transmission electron microscopy, x-ray photoelectron spectroscopy, and electron energy-loss spectroscopy indicated that Co element was incorporated into TiO2 to form Ti1−xCoxO2 compound. The direct evidence for the compositional inhomogeneity of the Ti1−xCoxO2 compound was given. Room temperature ferromagnetism with high magnetization was obtained, which could be attributed to the intrinsic properties of the amorphous magnetic semiconductor. The electrical transport in a low temperature range was explained by spin-dependent Efros’s variable range hopping, and correspondingly an exponential function of the magnetoresistance versus T−1∕2 was found.