[ Background] Black soil region is one of important grain production bases in China.However, the decrease of crop production has been obvious due to soil erosion by long-term cultivation.Previous researches focused on impacts of erosion on aboveground biomass and yields by using pot, pool or plot experimental methods, and paid little attentions to impacts on root growths. This study is to clarify the response of aboveground biomass, yields, root growths and their relationships to eroded black soils.[Methods] Both moderately and severely eroded black soil fields in Heshan farm of Heilongjiang Province were selected for the study, and the aboveground biomass dry weight (BDW ), leaf area index (LAI), and root growths every 10 days during different growth stages for maize and soybean in 2014 and 2015 were measured, and yields were obtained during the harvest time. A root sampling method of 5 holes for each soil layer with 15 cm depth by using a soil auger was proposed, and the root biomass and length were measured after washing root samples. [Results] The soil erosion significantly reduced the yield of maize and soybean. Compared with moderately eroded soil, severe erosion caused the reduction of yield by 32.7% for maize, and 57.1% for soybean. Soil erosion caused more obvious effects on the aboveground biomass, especially during the reproductive period, comparing with impacts on root growth. Severe erosion caused the decrease of BDW by 20.5% and 51.4% for maize during the middle and later growth respectively, and 21.9% and 55.7% for soybean, relative to moderately eroded soil. The growing rate of BDW also was more sensitive to soil erosion than that of RMD. From view of the impacts of erosion on the relationship between aboveground and underground biomass, the root shoot ratio increased with more severe erosion. The root shoot ratios of maize increased by 42.4%, 25.8%, 57.1% during the early,middle and later growth stages relative to the moderate soil erosion condition, and creased by 62%,54.2%, 85% during the early, middle and later growth stages for soybean. The percentage of root biomass to total root depth for two crops declined exponentially with soil depth. The percentage of root dry weights within the 0 ~15 cm deep soil layer to total root depths were more than 90% and 85% for maize and soybean respectively. Of two eroded soils, the percentage of root biomass of the surface layer to the total root depth was higher in moderately eroded soil than that in severely eroded soil. [Conclusions] This study indicated that crops adapted to harsh soil environment by developing their roots for absorbing more nutrients and moisture. This study also provided a method for sampling root, and explained the impact mechanism of eroded black soil on crop yields from the view of root growth and its relations to aboveground biomass. The results provide a reference for crop study in this region and lay a foundation for crop model research to modify the crop growth in the nature.