[en] Melt-spun ribbons of Nd-Fe-Co-B-C system alloys were prepared by the single roller rapid-quenching method. The effects of composition, substrate surface velocity, and heat treatment on the magnetic properties were studied. A maximum energy product of 140.5 kJ/m³ was obtained for Nd₁₁Fe₇₂Co₈(B_0.5C_0.5)₉ alloy ribbon prepared at a substrate surface velocity of 17.1 m/s. The amorphous Nd₁₁Fe₇₂Co₈(B_0.5C_0.5)₉ ribbons prepared at a substrate surface velocity of 20.7 m/s were crystallized by heat treatment, and the optimum annealing condition was found to be at 600 degree C for 30 min. Then the value of (BH)_max was 138.5 kJ/m³. The value of (BH)_max for a Nd₁₁Fe₇₂Co₈(B_0.5C_0.5)₉ bonded magnet prepared by using the ribbons heated at 600 degree C was 90.4 kJ/m³