The effects of the addition of Si on the temperature dependence of the electrical resistance and crystallization temperature, T x, of GeTe films were investigated by a two-point probe measurement. T x of the (GeTe) 100xSi x films increased with increasing Si content from x=0 (188°C) to x=12.6at% (297°C). It was confirmed from XPS measurements that Si-Te bonds were formed in the (GeTe) 100xSi x amorphous film by the addition of Si. The dependence of Si content on the T x of the (GeTe) 100xSi x film was calculated based on Lankhorst's model, which showed a linear relationship between T x and the Si content. In the region of low Si content (x ≤ 3.8at%), the obtained result was in good agreement with the calculated result. Meanwhile, in the region of high Si content (x ≥ 5.4at%), the obtained result considerably deviated from the calculated line. This may be due to the formation of the strongest Si-Si bonds in the amorphous (GeTe) 100xSi x film. It was found from XRD measurement that the (GeTe) 87.4Si 12.6 amorphous film showed crystallization with phase separation into α-GeTe and Si. The obtained results suggested that suitable Si content of the (GeTe) 100xSi x film is in the range 3-7at% because of the high T x, a small temperature interval of crystallization and the absence of phase separation during crystallization.