The invention provides a low-internal-heat solid laser amplifier. The low-internal-heat solid laser amplifier comprises a gain medium, a long-wavelength pumping light generating module and a long-wavelength pumping light control module, wherein the long-wavelength pumping light generating module comprises a pumping source, working substance and a resonant cavity; the pumping source is located outside the resonant cavity; the working substance is positioned in the resonant cavity; the long-wavelength pumping light control module is positioned in a long-wavelength pumping light oscillation pathin the resonant cavity in the long-wavelength pumping light generating module, wherein the light emitted by the working substance in the long-wavelength pumping light oscillation path directly entersthe side face of the gain medium; and the gain medium penetrates through the long-wavelength pumping light oscillation path.