Crystallographic and magnetic properties of the Nd14Fe78B8-xCx compounds were investigated. The properly annealing treatment was found to be the condition that the compounds of light rare earth-iron-carbon belonging to the P42/mnm type structure could be formed. The magnetic ordering temperatures of the compounds decreased somewhat with increasing the carbon concentration, but the saturation magnetization σs had a gentle maximum, and the residual ma gnetization σr, intrinsic coercivity iHe as well as the anisotropy field Ha at room temperature showed a significant increase. The anisotropy behaviours of the C-containing samples were similar to Nd-Fe-B. The fact that the transition temperatures of spin reorientation gradually descended with increasing the carbon content while the canting angle at 1.5 K had a slight increase suggested that there was complicate coupling between the anisotropies of Nd and Fe sublattices. In addition, the suitably Nd-rich carbide exhibited relatively large anisotropy.