Abstract: The purpose is to describe the design and the construction of a no-flow conventional CW CO2 laser with line selected by concave grating.In order to obtain the lines at 11μm wavelength region,a concave grating(150lines/mm,blazed at 10.6μm) with a 10m radius curvature and a longer cavity(4.5m) is employed to increase the resolution of the cavity without a hot CO2 absorption cell in the cavity.In this laser,besides more than 100 laser lines observed from R(56) to P(56) in the regular 0001-1000,0200Ⅰ,Ⅱ band,another 16 lines in 11μm wavelength region including 7 lines in the 0111-0310 band,1 line in the 0011-1110 band,5 lines in the isotope C13O2160001-1000 band and 3 lines in the isotope C13O2180001-1000 band,are also observed.The output power of every line is above 1.6W.