In order to understand the molecular genetic mechanism of yield-related traits and identify markers/genes in sunflower, QTL mapping and candidate gene identification of yield-related traits were performed using 150 individuals derived from recombinant inbred line (RIL) population of K55×K58 combination. The phenotype data at two environmental conditions in 2019 and 2020 were producted, and the high-density linkage map of SNP molecular markers were deployed. The results showed that nine QTL (LOD≧2) for 8 traits including plant height, stem thickness, number of leaves, number of grains particles, grain weight, number of empty grains particles, 100-seed weight, and seed setting rate were detected, in which QTL loci at stem diameter (Qsd17, Qsd9) and 100-grain weight (Qhgw8 and Qhgw5) were detected at two environmental conditions. A multi-genic effect site (Qsd17, Qngp17) controlling the number of grains and stem thickness was detected. These QTL loci were found on chromosomes 4, 5, 7, 9, 13, 14, 16 and 17, and the contribution rate of phenotypic variation was 0.265%-13.075%. There were two main effect loci (Qngp17 and Qhgw8) with phenotypic contribution over 10% on chromosome 17. Fourteen candidate genes were annotated in QTL loci with stable or main effect (PVE>10%), These genes are involved in carbohydrate processes and cell wall/membrane/envelope biogenesis, and annotated such as NADH dehydrogenase, E3 ubiquitin protein ligase, SAUR family proteins, MADS-box transcription factors, MYB family transcription factors. Collectively, these results might provide theoretical basis for sunflower high-yield breeding.