Abstract: To clarify the effects of nitrogen and intrusion degree of Flaveria bidentis on maize growth, four nitrogen levels and four mixed planting proportions of maize/Flaveria bidentis were set to study the changes of maize growth, photosynthesis and yield under different treatments. The results showed that under different growth stages, plant height, stem diameter and LAI of maize changed significantly with the planting density increase of Flaveria bidentis, and the difference was also influenced by nitrogen levels. The SPAD value and net photosynthetic rate of maize at different growth stages were also affected by the nitrogen application gradients and the density of mixed planting. The effects of the mixed planting on maize yield changed with the increase of nitrogen application. When the maize/Flaveria bidentis mixed planting proportion reached 2:1 (A2) and the nitrogen application rate reached 175 kg/hm2 (T1), the Flaveria bidentis mixed planting had significant effect on maize yield. The combined effect of mixed planting and nitrogen levels on maize growth and photosynthetic indexes varied with its development of growth periods. At maturing stage of maize, the effect of mixed planting and nitrogen application on maize yield had notable interaction.