An excimer laser composite cavity, comprising a laser discharge cavity, which contains work gas for generating a laser beam when it is activated by an excitation source, and a laser output module, the excimer laser composite cavity further comprising a line-width narrowing module (3,5) and a laser amplification module, wherein: the laser discharge cavity, the laser output module, and the line-width narrowing module (3,5) constitute a line-width narrowing cavity configured to narrow down a line-width of the laser beam generated by the work gas; the laser discharge cavity, the laser output module, and the laser amplification module constitute an amplification cavity configured to amplify power of the laser beam with the line-width having been narrowed down by the line-width narrowing cavity; and the laser output module is configured to output the laser beam having a narrowed line-width and amplified power, wherein the laser discharge cavity has two ends, wherein the laser output module is arranged at one end, and the line-width narrowing module (3,5) and the laser amplification module are arranged at the other end; wherein the line-width narrowing module (3,5) comprises a single prism or a prism group and a grating, wherein the single prism or prism group is configured to receive the laser beam emitted from the laser discharge cavity, reflect a part of the laser beam to the amplification cavity, refract and expand a remaining part of the laser beam, and emit the expanded laser to the grating; and the grating is configured to receive the expanded laser beam emitted from the single prism or prism group at an incident angle equivalent to a blazing angle of the grating, so that the laser beam incident on a surface of the grating is dispersed and a laser beam with a wavelength meeting a blazing condition of the grating is reflected back along an opposite direction of its incident path, wherein the laser amplification module comprises a reflector configured to receive the part of the laser beam reflected by the single prism or prism group, and reflect the part of the laser beam back to the laser discharge cavity along an opposite direction of its incident path, and wherein the amplification cavity further comprises an etalon configured to narrow down the line-width of the laser beam incident thereon and transmit laser beam with a particular central wavelength. the laser discharge cavity, the laser output module, and the line-width narrowing module (3,5) constitute a line-width narrowing cavity configured to narrow down a line-width of the laser beam generated by the work gas; the laser discharge cavity, the laser output module, and the laser amplification module constitute an amplification cavity configured to amplify power of the laser beam with the line-width having been narrowed down by the line-width narrowing cavity; and the laser output module is configured to output the laser beam having a narrowed line-width and amplified power, wherein the laser discharge cavity has two ends, wherein the laser output module is arranged at one end, and the line-width narrowing module (3,5) and the laser amplification module are arranged at the other end; wherein the line-width narrowing module (3,5) comprises a single prism or a prism group and a grating, wherein the single prism or prism group is configured to receive the laser beam emitted from the laser discharge cavity, reflect a part of the laser beam to the amplification cavity, refract and expand a remaining part of the laser beam, and emit the expanded laser to the grating; and the grating is configured to receive the expanded laser beam emitted from the single prism or prism group at an incident angle equivalent to a blazing angle of the grating, so that the laser beam incident on a surface of the grating is dispersed and a laser beam with a wavelength meeting a blazing condition of the grating is reflected back along an opposite direction of its incident path, wherein the laser amplification module comprises a reflector configured to receive the part of the laser beam reflected by the single prism or prism group, and reflect the part of the laser beam back to the laser discharge cavity along an opposite direction of its incident path, and wherein the amplification cavity further comprises an etalon configured to narrow down the line-width of the laser beam incident thereon and transmit laser beam with a particular central wavelength.