Three series of amorphous Ge 1 0 0 - x - y Pb x S y thin films with y = 56.5, 63 and 70 were prepared by flash evaporation. Light-induced phenomena such as photodarkening (PD) and light-induced electron paramagnetic resonance (LEPR) were examined under various conditions. There is no obvious relationship between the PD and the LEPR, showing that the PD does not originate from the bond breaking. The PD gradually disappears with Pb incorporation. X-ray photoelectron spectroscopy study and the decrease in √B, which is the slope of the Tauc plot, with illumination revealed that the disappearance of the PD in Pb-incorporated Ge-S films is mainly caused by the tightening of the network structure with Pb incorporation. The disappearance of the LEPR results from other modifications of the network structure. The electrical and optical properties of amorphous Ge 1 0 0 - x - y Pb x S y thin films are also discussed.