To harness elite genetic resources from Gossypium mustelinum L. for the genetic improvement of upland cotton， a backcross introgression line （BC₅S₅） population comprising 71 lines was developed. This population was derived using Gossypium hirsutum B0011 as the recurrent parent and G. mustelinum as the donor parent. Phenotypic evaluation and quantitative trait locus （QTL） mapping were conducted for eight fiber quality traits （fiber length， fiber strength， micronaire value， maturity of cotton fiber， fiber uniformity， short fiber content， fiber elongation， and the water content） and three yield traits （lint weight， single boll weight， and lint percentage）. The results indicated that lint weight and short fiber content are strongly influenced by genotype， while fiber length， fiber strength， fiber uniformity， fiber elongation， micronaire value， and lint percentage are more significantly affected by environmental conditions. Maturity of cotton fiber and water content are more affected by genotype×environment interaction than genotype. Most yield traits show weak correlations with fiber quality traits， but single boll weight and lint percentage are still significantly influenced by fiber quality traits. Among these， single boll weight exhibits significant correlations with micronaire value and fiber elongation， while lint percentage shows a significant correlation with water content. A total of 80 QTLs were identified， including 63 associated with fiber quality and 17 with yield traits， distributed across 21 chromosomes. A high proportion of these QTLs exhibited high contribution rates， with over 80% having a LOD value greater than 3.00 and high linkage recombination rates. Notably， five QTLs （qLW-A06-1， qMCF-A12-1， qFS-A13-1， qSW-A10-1， and qSW-D06-1） were stably detected across multiple environments. Furthermore， four pleiotropic loci （A10：88383565， D06：36287101， D06：55819963， and D13：60179605） were identified， all linked to short fiber content （SFC）. Eight QTL clusters were detected on chromosomes A01 （two clusters）， A10 （two）， A13 （one）， D04 （one）， and D06 （two）， each regulating multiple fiber quality and yield traits. The results of this study provide potential application value for cotton molecular breeding practice.