Abstract: The legume/cereal intercropping system, supplying the world with most of the grain and proteins, is one of the most successfully farming systems for small-holder farmers. It is undoubtedly a sustainable farming system from both resources use and environmental friendly aspects as the nitrogen fixed by legumes sustains this system. Internationally, research effort has been focused on biological nitrogen fixation in legume/graminaceae systems due to environmental problems and energy crisis caused by irrational N fertilizer use. The change of light intensity, light transmittance, soil nutrients, corn grain yield, alfalfa yield and income of the system of corn intercropping with alfalfa were studied. Light intensity and light transmittance of different parts increased as the row space changed from narrow to wide, and in all treatments they were higher than in the CK except in T4. The contents of organic matter, organic nitrogen and available nitrogen of intercropping treatments displayed an increasing trend compared with those of the CK, and the trends became increasingly obvious with successive intercropping years. The contents increased with row space. With the same corn number per hectare, the maximum corn grain yield was achieved in T2 treatment for 3 years, and in all treatments it was higher than in the CK except for T4. Alfalfa yield increased with row space. Reduced N use resulted in reduced maize yield of various degrees, and yield declined with intercropping year, but there was no significant difference of yield between R1, R2, and CK in 2008.