Abstract: 【Objective】The study aimed to study the quality changes during the berry growth and development of wine grape variety Marselan ，and to identify key genes regulating growth，development，and berry quality，providing theoretical basis for the precise formulation of cultivation practices and the improvement of berry quality.【Method】Marselan grapes from the eastern foothills of Helan Mountain were used as experimental materials. Grape berries were collected at 20，45，75 and 100 d after flowering at different developmental stages. The transverse and longitudinal diameters of the berries were measured，and the contents of soluble solids，total sugar，titratable acid and total phenolics were determined.Transcriptome sequencing analysis was also conducted.【Result】As the Marselan grape berries developed，their color deepened and berry size increased. The berry soluble solid content and total sugar content gradually rose，while the titratable acid content gradually decreased. The total phenolic content decreased from 20 d to 75 d after flowering，but slightly increased between 75 d and 100 d after flowering. A total of 33517 DEGs were identified among grape berries at different developmental stages，with 3976 DEGs shared between the comparison groups of 45 d after flowering versus 20 d after flowering，75 d after flowering versus 45 d after flowering，and 100 d after flowering versus 75 d after flowering. The results of GO functional annotation analysis showed that the DEGs in each comparison group were mainly annotated to functional categories such as organelles，cell membranes，protein-containing complexes，cellular processes and metabolic processes. The results of KEGG signaling pathway enrichment analysis showed that amino acid biosynthesis，glycolysis/gluconeogenesis and flavonoid biosynthesis were important signaling pathways during the development of Marselan grape berries. Among the DEGs enriched in the flavonoid biosynthesis signaling pathway，it was found that the chalcone synthase gene（CHS）and flavanone-3-hydroxylase gene（F3H）were up-regulated from 45 d to 75 d after flowering and down-regulated from 75 d to 100 d after flowering，suggesting that the CHS and F3H genes played important regulatory roles in the coloration of Marselan grape skin.【Conclusion】The growth and development of Marselan grapes are accompanied by the deepening of fruit color，enlargement of berry size，and dynamic changes in biochemical components. The flavonoid biosynthesis signaling pathway plays an important role in the color transition process of grapes，and the CHS and F3H genes have influence on the coloration and quality formation of Marselan grape berries.