The optical absorption edges of amorphous As 2S 3 films shifted to lower energy with band gap light illumination or annealing near the glass transition temperature. The magnitude of red shift increased with the increase of the intensity of illumination light and the time of illumination and became saturated finally. The red shift in well annealed As 2S 3 film was reversible. Photocrystallization was also observed in the illuminated As 2S3 films with scanning electron microscope (SEM) measurements and the crystal phase was more with higher intensity of illumination light. The photoinduced effects in amorphous As 2S3 films were ascribed to photostructural changes and the change mechanisms are discussed in this paper.