Abstract: 【Objectives】A root barrier technique was attempted to investigate the difference of growth and nitrogen uptake of maize which was relay intercropped with legume and convolvulaceae crops, the yield increase mechanism of intercropping system on maize would be explored.【Methods】 Water culture experiment was carried out with 23 randomized complete block design. Maize was relay intercropped with soybean and sweet potato separately, three root partitions (no partition, partial root partition and complete root partition) were used. The root activity, root dry matter, leaf photosynthetic characteristics, grain yield and N uptake were investigated. 【Results】 1) The relay intercropping patterns significantly affected on maize growth (P0.05). The root activity, grain weight and above-ground total N uptake of maize were 6.25%, 8.69% and 18.89% significantly higher when relay intercropped with soybean than with sweet potato under without root barrier treatment, respectively. However, the differences were not significant under root barrier treatments (P0.05). 2) The dry matter accumulation and grain yield of maize were affected by the root barrier treatments, showing order of no root partitionpartial root partitioncomplete root partition. 3) No root partition treatment could improve the growth of intercropped maize. In maize-soybean intercropping, the root activity, photosynthetic rate, grain yield and total N uptake of maize were higher in treatments of without root partial than with barrier, their differences were 25.65%, 28.45%, 64.69% and 71.65%, respectively. In maize-sweet potato relay intercropping, their differences were 17.59%、 19.83%、 52.38% and 46.21%, respectively. 4) The root biomassis positive significantly correlated with the above-ground biomass, the photosynthetic rate and the grain yield, the correlation indexes are 0.984, 0.927 and 0.986, respectively(P0.01). The root activity is positive significantly correlated with photosynthetic rate, the correlation index is 0.929 (P0.01). 【Conclusions】The root activity, photosynthetic rate, biomass, grain yield and total N uptake of maize can significantly increased, which contributed to the high yield and N uptake of maize. The increase effects are higher when maize are intercropped with soybean than with sweet potato.