This experiment was carried out to compare chemical composition, TDN yield of corn-soybean intercropping and corn monocropping forage plants at different harvesting time and obtained the following results. 1. In both cropping systems, the content of chemical composition of forage were changed same pattern in growing stage. The content of crude protein in corn-soybean intercropping forage at yellow stage increased more than that of corn nonocropping forage, while the crude fat in corn monocropping forage plants increased than that of corn-soybean intercropping forage plants at mature stage. 2. The crude fiber, crude ash, ADF content of forage plants in both cropping system decreased same pattern in growing period, however, NFE content of forage increased with maturity. 3. TDN yield of corn-soybean intercropping and corn monocropping forage plants at yellow stage obtained similar results and TDN yield per 10a in intercropping and monocropping were 1006.lkg and 978.6kg, respectively. 4. Consequently, corn-soybean interaopping system could be increased crude protein yield without decreasing of dry matter yield in comparison with corn monocropping system for corn silage.