Soil compaction is the main form of soil degradation in agricultural systems. It leads to decreased infiltration and limited root growth. Plants can alleviate soil compaction through various mechanisms connected to root growth. However, it remains unclear whether plant breeding can improve the root traits of modern cultivars and their ability to alleviate compacted soil. The aim of this study was to determine the responses of soybean (Glycine max L. Merr.) roots to soil compaction and to observe the difference in soil alleviation by using soybean varieties bred before and after the development of mechanical agriculture in the Mollisol region of Northeast China. Five soybean varieties, bred from 1941 to 2003, were planted and subjected to either soil compaction or no compaction. Root traits and soil macropores were characterised by screening the root system (Shovelomics method) and by adopting dye-tracing methods. The properties of roots in soybean varieties showed noteworthy differences, although no clear breeding trends were detected. Compared with no compaction, the root lengths of all varieties decreased significantly when grown in compacted soil. Moreover, soil compaction decreased the vertical macroporosity and increased the heterogeneity of horizontal macropores. The modern soybean variety alleviated soil compaction by enabling the creation of more macropores, which were located deeper in the soil, compared to the older varieties. Overall, root growth was responsible for approximately one-third of macropore changes observed under compacted soil conditions, and the alleviation effects were greater in roots growing vertically than those observed in roots growing laterally. The observed variability of soil compaction alleviation among different soybean varieties could be considered in agriculture by breeders to select the varieties which decrease soil compaction.