Using electron microscopy and electron diffration methods, we have investigated the microstructures, shortrange order and their changes with increasing temperature in amorphous Tb31Fe69 and Tb27Fe73 films prepared by vapour deposition in a vacuum of 10-5 torr. The process of crystallization have also been observed and analysed. The microstructures of samples with different oxygen contamination and different annealing temperatures were found to be different. However, the phase separation of both samples seemed to occure by a mechanism similar to spinodal decomposition, by which an initial amorphous phase first decomposed into two or more compsitionally discrete amorphous phase, each of which then crystallized independently with rising temperature. Thus, the whole process of crystallization consisted of several stages. Finally a poly-crystalline mixture would be formed.