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 (3, 5), 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 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 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 with high reflectivity to the pump light at 880 nm-980 nm and a second dielectric film with high transmittance at 1020-1080 nm, or the dielectric film B (5-1, 5-2) having a first dielectric film with high reflectivity at 880 nm-980 nm and a second dielectric film 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 (3, 5), 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 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 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 with high reflectivity to the pump light at 880 nm-980 nm and a second dielectric film with high transmittance at 1020-1080 nm, or the dielectric film B (5-1, 5-2) having a first dielectric film with high reflectivity at 880 nm-980 nm and a second dielectric film with transmittance at 980-1100 nm.