The studies of the dc-electric field induced second harmonic generation (SHG) for fundamental wavelength of the Ag 2 S–Ga 2 S 3 –P 2 S 5 using nanosecond Er:glass laser at wavelength 1540nm and elevated temperatures (thermal poling) were performed. We have found that the highest output SHG efficiency is obtained for the maximal Ga 2 S 3 content and with simultaneous presence of Ag 2 S. We have shown that the SHG effect exists only during simultaneous dc- and thermal poling at about 120°C. After switching off of the dc-electric field the effect is completely reversible. The maximally achieved value of the effective second-order optical susceptibility is equal to about 0.75pm/V at 1540nm wavelength, which allows to propose to apply these materials for the laser operation.