The extremely early-maturing maize production region is one of the major commercial grain production bases in China. In recent years, increasing planting density to improve the yield of extremely early-maturing maize has become increasingly difficult, making the improvement of yield per plant an important strategy for overcoming the bottleneck of high yield. However, studies on the genetic loci associated with ear-related traits in extremely early-maturing maize remain limited. In this study, a doubled haploid (DH) population was developed through haploid technology using a cross between the extremely early-maturing inbred line CAVA119 and the medium-early-maturing inbred line 2104133005. Genotyping was performed using the Maize 3K liquid SNP chip. QTL mapping analyses for ear-related traits, including ear length, ear diameter, kernel row number, and kernel number per row, were conducted in the DH population and corresponding testcross populations across three different environments. A total of 86 QTLs associated with ear-related traits were identified. In the DH population, 55 QTLs were detected, including 17, 16, 15, and 7 QTLs associated with ear length, ear diameter, kernel row number, and kernel number per row, respectively. The major-effect locus was qKNPR1-2, with a LOD score of 22.02 and a phenotypic variation explained (PVE) of 12.02%. Among these, 18 yield-increasing alleles were derived from the extremely early-maturing parent CAVA119. In the testcross population, 31 yield-related QTLs were identified, including 8, 14, 5, and 4 QTLs associated with ear length, ear diameter, kernel row number, and kernel number per row, respectively. Among these, 11 yield-increasing alleles were contributed by the extremely early-maturing parent CAVA119. In addition, six QTLs identified in the testcross population overlapped with those detected in the DH population. Furthermore, two novel loci showing stable expression across multiple environments, qEL7-1 and qKNPR7-1, were identified. This study provides important theoretical insights and valuable genetic resources for elucidating the genetic basis of yield-related traits in extremely early-maturing maize and for advancing molecular breeding efforts.