Abstract: Taking cucumber cultivar ‘Jinchun 4’ as test material, a pot experiment was conducted to study the effects of soil compaction stress on cucumber root growth, respiration rate, activity, and nitrogen metabolism at different development stages. Two treatment were installed, i.e., bulk density 1.25 g·cm^-3 (loose soil, CK) and 1.55 g·cm-3 (compacted soil). Under the stress of soil compaction, the total root length, root surface area, root forks, and root tips at different development stages decreased significantly, the root elongation growth and lateral root emergence were constrained remarkably, but the root radial growth was stimulated and the root average diameter was significantly increased. Meanwhile, both the root activity and the respiration rate decreased significantly, the root NO₃^-, free amino acids, and soluble protein contents had a large decrease, the root nitrate reductase, glutamine synthetase, and glutamate synthase  activities decreased significantly, whereas the root NH₄⁺ content had a significant increase. All the results indicated that under the stress of soil compaction, the uptake of nitrate by cucumber roots decreased, the nitrogen assimilation was inhibited, and the nitrogen metabolism was remarkably constrained.