The carbon and nitrogen atoms can be introduced into the R_2Fe_(17) structure by a proper heat treatment.The crystallographic and intrinsic magnetic properties of a series of R_2Fe_(17)CN_x,where R=Y,Sm,Gd,Tb,Dy,Er have been investigated by using X-ray diffraction technique and magnetic measurements.The interstitial car-bon and nitrogen atoms are found to have an effect of dilating unit cell volume,raising Curie temperature andsaturation magnetization,as well as enhancing uniaxial magnetocrystalline anisotropy. The carbon and nitrogen atoms can be introduced into the R_2Fe_ (17) structure by a proper heat treatment. The crystallographic and intrinsic magnetic properties of a series of R_2Fe_ (17) CN_x, where R = Y, Sm, Gd, Tb, Dy, Er have been investigated by using X-ray diffraction technique and magnetic measurements. The interstitial car-bon and nitrogen atoms are found to have an effect of dilating unit cell volume, raising Curie temperature and saturation magnetization, as well as enhancing uniaxial magnetocrystalline anisotropy.