Abstract: Effect of spraying leaves with a boron fertilizer of different concentrations on the growth of roots and plant of low-yield Fengtian 1 common buckwheat were studied. The correlation between aboveground， underground and yield was analyzed，also. With the spraying，the available phosphorus，available potassium in rhizosphere soil and root length，root surface area and root volume was increased，while the content of organic matter in rhizosphere soil and the number of nodes and branches of main stem were significantly decreased. The application of boron fertilizer had little effect on pH in rhizosphere soil and mean diameter of root of Fengtian 1. When the boron concentration was at 24 mg/L，the yield of common buckwheat reached the maximum，what increased yield by 42.18% compared to the control. Correlation study showed that there was a significant positive correlation between root length and root surface area，and there was a significant positive correlation between root surface area and root volume，and there was a significant negative correlation between the root volume and the number of branches of the main stem，which had significant negative correlation with the number and yield of the main stem，and there was a significant negative correlation between root mean diameter and the number of main stem nodes，and there was an extremely significant positive correlation between plant height and the number of branches in the main stem，and there was a significant positive correlation between the number of branches of main stem and the number of nodes of main stem.