With the pulsed laser deposition(PLD) method, amorphous 80GeS 2-15Ga 2 S 3-5CdS chalcogenide film was deposited on glassy substrate. Obvious second harmonic generation(SHG) was observed in the ultraviolet(UV)-polarized film and the SHG intensity increased with the increase in single pulse energy and irradiation time. Through Raman spectra and transmission spectra, the mechanism of SHG was studied. The experimental results demonstrated that effective electron traps and hole traps were generated in the UV- polarized film. The energy of electrons and holes was using up due to the collision with other particles and crystal fields during their movement and finally they were captured by the traps and fixed, which made the electric charge distribution nonuniform in the film and destroyed the spatial isotropy. In the meantime, the center of positive and negative charges separated and a built-in electric field was formed which generated the optical second-order nonlinearity of the film. With the pulsed laser deposition (PLD) method, amorphous 80GeS 2-15Ga 2 S 3-5CdS chalcogenide film was deposited on glassy substrate. Obvious second harmonic generation (SHG) was observed in the ultraviolet (UV) -polarized film and the SHG intensity increased with the increase in single pulse energy and irradiation time. Through Raman spectra and transmission spectra, the mechanism of SHG was studied. The experimental results of that effective electron traps and hole traps were generated in the UV-polarized film. The energy of electrons and holes was using up due to the collision with other particles and crystal fields during their movement and finally they were captured by the traps and fixed, which made the electric charge distribution nonuniform in the film and destroyed the spatial isotropy. center of positive and negative charges separated and a built-in electric field was formed which generated the optical second-order nonlinearity of the film.