Waxy maize (Zea mays L. ceratina) is extensively cultivated and exhibits substantial market demand in China; however, its yield and quality improvement remain constrained by relatively underdeveloped cultivation techniques. Optimizing plant density and row spacing is critical to improving the yield and nutritional quality of waxy maize, yet their combined effects remain insufficiently explored. A split-plot design evaluated two plant densities, i.e., 5.25 × 10⁴ plants ha⁻¹ (PD_5.25) and 6.75 × 10⁴ plants ha⁻¹ (PD_6.75), and three row configurations, i.e., 80 + 40 cm wide–narrow rows (RS_8-4), 100 + 20 cm wide–narrow rows (RS_10-2) and conventional 60 + 60 cm equal rows (RS_6-6). This study aims to identify the optimal cultivation configuration for waxy maize in the Loess Plateau region. Results showed that the RS_8-4 configuration maximized agronomic traits, dry matter accumulation, and yield relative to RS_6-6 and RS_10-2 treatments. Specifically, RS_8-4 reduced the insertion angle of the lower ear leaf by 12.4% (p < 0.05) and ear height by 8.3% while increasing yield by 19.86–20.00% compared to RS_6-6 and RS_10-2 treatments. At fresh-market maturity, dry matter accumulation under RS_8-4 treatment increased significantly by 34.0% with higher plant density. Under PD_6.75, RS_8-4 boosted dry matter by 29.8% and 39.4% versus RS_6-6 and RS_10-2, respectively. Under the RS_8-4 and PD_6.5 configurations, dry matter accumulation reached 13.56 t ha⁻¹ and a yield of 9.94 t ha⁻¹ was achieved in 2022. In summary, the combination of the PD_6.75 density and the RS_8-4 row spacing configuration achieved the optimal yield for the ‘Jinnuo 20’ cultivar in the Loess Plateau region. This approach provides a scalable planting framework for high-yield waxy maize production in the area, while demonstrating that optimized plant density and row spacing represent not only a key technical measure for enhancing productivity but also a core agronomic strategy for improving resource-use efficiency.