An all-solid-state high-power slab laser based on phonon band-edge emission, which is comprised of a pumping source , a focusing system , a resonant cavity and a self-frequency-doubling crystal in the resonant cavity; in which the said pumping source , focusing system and resonant cavity are successively arranged along the optical path, and the said resonant cavity is located at the output end of the said focusing system ; in which the said self-frequency-doubling crystal is a Yb-doped RECOB crystal; The resonant cavity is comprised of an input cavity mirror and an output cavity mirror , in which the said input cavity mirror and the output cavity mirror are respectively coated with a dielectric film , to suppress the starting laser oscillation at the band of 1020-1080 nm and realize the starting laser oscillation at the band of 1120-1200 nm; wherein The said self-frequency-doubling crystal is cut into slab shape along the direction of the crystal's maximum effective nonlinear coefficient; The said pumping source is a diode laser matrix at 880 nm-980 nm, and the pump light emitted by the said pumping source forms a rectangular spot through the said focusing system and is focused on the light transmission face of the self-frequency-doubling crystal in the said resonant cavity; the said light transmission direction is the lengthwise direction of the slab-shaped crystal, wherein the input cavity mirror is formed by coating the input cavity mirror with a dielectric film A (3-1, 3-2), the dielectric film A (3-1, 3-2) having a dielectric film (3-1) with high transmittance to the pump light at 880 nm-980 nm and at 1020-1080 nm, or the dielectric film A (3-1, 3-2) at least having a dielectric film (3-1) with high transmittance at 880 nm-1100 nm; and wherein the output cavity mirror is formed by coating the output cavity mirror with a dielectric film B (5-1, 5-2) having a first dielectric film (5-1) with high reflectivity to the pump light at 880 nm-980 nm and a second dielectric film (5-2) with high transmittance at 1020-1080 nm, or the dielectric film B (5-1, 5-2) having a first dielectric film (5-1) with high reflectivity at 880 nm-980 nm and a second dielectric film (5-2) with transmittance at 980-1100 nm. The resonant cavity is comprised of an input cavity mirror and an output cavity mirror , in which the said input cavity mirror and the output cavity mirror are respectively coated with a dielectric film , to suppress the starting laser oscillation at the band of 1020-1080 nm and realize the starting laser oscillation at the band of 1120-1200 nm; wherein The said self-frequency-doubling crystal is cut into slab shape along the direction of the crystal's maximum effective nonlinear coefficient; The said pumping source is a diode laser matrix at 880 nm-980 nm, and the pump light emitted by the said pumping source forms a rectangular spot through the said focusing system and is focused on the light transmission face of the self-frequency-doubling crystal in the said resonant cavity; the said light transmission direction is the lengthwise direction of the slab-shaped crystal, wherein the input cavity mirror is formed by coating the input cavity mirror with a dielectric film A (3-1, 3-2), the dielectric film A (3-1, 3-2) having a dielectric film (3-1) with high transmittance to the pump light at 880 nm-980 nm and at 1020-1080 nm, or the dielectric film A (3-1, 3-2) at least having a dielectric film (3-1) with high transmittance at 880 nm-1100 nm; and wherein the output cavity mirror is formed by coating the output cavity mirror with a dielectric film B (5-1, 5-2) having a first dielectric film (5-1) with high reflectivity to the pump light at 880 nm-980 nm and a second dielectric film (5-2) with high transmittance at 1020-1080 nm, or the dielectric film B (5-1, 5-2) having a first dielectric film (5-1) with high reflectivity at 880 nm-980 nm and a second dielectric film (5-2) with transmittance at 980-1100 nm. <EOS>