In this study, non-compacted and compacted treatments of red soil were established in Jinggangshan Agricultural High-Tech Zone, Ji'an City, Jiangxi Province, and different summer cover crops (soybean, sesbania, and sudangrass) and maize relay intercropping experiments were conducted with monocropped maize as a control (CK), to analyze the response of different cover crops and maize relay intercropping to compacted red soil. The results showed that soil compaction limited soybean root growth with a 26% reduction in total root length. In contrast, sudangrass had a greater root diameter and was less affected by soil compaction. Under non-compacted conditions, soil water content increased by 16% and 21% in maize relay intercropped with sudangrass compared to in maize relay intercropped with sesbania and soybean, respectively. Additionally, maize relay intercropped with sudangrass, sesbania or soybean significantly increased above-ground biomass of maize compared to CK. Among these, maize relay intercropped with soybean promoted the uptake of available nitrogen by maize and resulted in the reduction of alkali-hydrolyzable nitrogen content of the soil by 22%, and its above-ground biomass of maize was the highest. Under compacted conditions, maize relay intercropped with sesbania or soybean significantly increased maize above-ground biomass relative to CK, while maize relay intercropped with sudangrass did not significantly promote maize growth, and soil compaction did not significantly affect maize above-ground biomass under maize relay intercropped with sudangrass compared to maize relay intercropped with sesbania or soybean. Therefore, in non-compacted soil, maize relay intercropped with soybean is a more suitable cropping pattern in the southern red soil area, which can promote maize growth. And in compacted soil, maize relay intercropped with sesbania or soybean can increase maize above-ground biomass, while maize relay intercropped with sudangrass is less sensitive to compacted red soil.