Cowpea is a legume crop that fixes atmospheric nitrogen with soil rhizobia. This study investigated the effects of nitrogen supply and light intensity on N2fixation and growth of rhizobia-inoculated cowpea. The hydroponic experiment designed to evaluate the response of cowpea inoculated with three Bradyrhizobium strains (TSC7, TSB2, TTC9) under different N concentrations (0, 1, 2.5, 5, 7.5, 10 mM) showed that regardless to the used inoculant, N ? 2.5 mM inhibit the nodulation and nitrogen fixation of cowpea at early stages (2-4 WAT). While the three strains similarly affect cowpea nodulation at 2 WAT, at later stages (4-6 WAT), the nodulation phenotype varied among them. At 6 WAT, N ? 2.5 mM did not repress the nodulation of TSC7- and TTC9-inoculated but rather improved it. This study shows that the supply of 1 mM N is beneficial in stimulating the nitrogen fixation of TTC9- and TSB2-inoculated cowpea, and at later stages, the nitrogen fixation inhibitory effect of N 2.5 mM and N 5 mMis decreased. In the second experiment, conditions of100, 75, 50and 25%light intensities of the natural light were set up in a glasshouse to study their effect on N2fixation and growth of cowpea inoculated with B. yuanmingense DTC8, TSC7, and TTC9 strains. The 100% and 75% light intensities led to better cowpea growth and production. The study shows that when the light intensity is decreased to 75% of the natural light (about 535? molm-2 sec-1PPFD), cowpea seed production and nitrogen content is improved. Appropriate lightning would therefore greatly improve the quantity and quality (protein) of cowpea seeds.