This experiment was carried out to compare chemical composition of corn-cowpea intercropping and corn monocropping plants at different harvesting time and obtained the following results. 1. In both cropping systems, the contents of crude fat and nitrogen free extract (NFE) were significantly increased (P<0.01), while that of crude protein, crude fiber and crude ash were decreased (P<0.01) with each harvesting time. 2. The acid detergent fiber (ADF) and crude fiber contents were decreased same patterns in growing period, however, according to maturing of corn ears the difference between ADF and crude fiber contents reduced. 3. At mature stage, crude protein yields per 10a in corn monocropping and corn-cowpea intercropping system were 127.6kg and 152.lkg, respectively. The difference of crude protein content between corn-cowpea intercropping and corn monocropping system was 19.2%. 4. TDN yields of each cropping system, at mature stage, obtained similar results and TDN yields per 10a of corn monocropping and corn-cowpea intercropping system were 1006.lkg and 990.1, respectively. 5. Conseqently, corncowpea intercropping system could be increased protein yield without decreasing of dry matter yield in comparison with corn monocropping system.