The experiment used the soybean variety Jiyu 86 which is not tolerant to dense planting and the soybean variety Changmidou 30 which is tolerant to dense planting as materials. Two treatments were set up in this experiment, one was planting mode treatment: double row planting on ridge and single row planting on ridge, the other one is the planting density treatment: 200,000 plants/ha and 400,000 plants/ha. To explore the physiological and morphological characteristics of underground root system and the quality and yield characteristics of above-ground dry matter of soybean varieties with different density tolerance characteristics. The results showed that root activity, root dry weight, root length, root surface area, root volume and root tip number were positively correlated with soybean yield and dry matter, respectively. High density planting significantly decreased the dry matter quality and yield of Jiyu 86, and the yield of Changmidou 30 was decreased but not to a significant level. The yield of Jiyu 86 increased significantly under high density conditions. High-density planting had a higher degree of competition inhibition on the underground root system and above ground canopy of the intolerant variety Jiyu 86. Double row on ridge had obvious optimization effect on root morphology of dense-tolerant soybean varieties, especially under high-density condition, the optimization effect was better than that of dense-tolerant soybean varieties. The underground root hierarchical structure of Changmidou 30 was more affected by planting pattern, and that of Jiyu 86 was more affected by planting density. In summary, the underground roots of dense-tolerant soybean varieties have a better ability to withstand competition inhibition and have a stronger responsiveness to root activity under high-density conditions,which is an important reason for the higher aboveground biomass and yield of dense-tolerant soybean varieties under high-density conditions.