Abstract: In order to investigate the genes controlling leaf size of Hemerocallis fulva and support subsequent genetic diversity analysis and improved species selection, we conducted transcriptome sequencing and assembly on two varieties of Hemerocallis fulva with different leaf sizes. A transcriptome library was constructed, followed by pathway analysis and functional annotation of differentially expressed genes. We obtained a total of 90,366 gene clusters(Unigenes), among which 10,671 Unigenes showed significant differences in expression quantity. These Unigenes accounted for 39.25% of the genetic sequences, with 6,483 genes upregulated(60.75%). By comparing these Unigenes with NCBI database and literature references related to leaf size regulation in Hemerocallis fulva, we identified a total of 678 potentially relevant genes. Further confirmation through qRT-PCR revealed that ARF2, BRI1, CESA3, CYP90, IAA4 are closely associated with leaf development in Hemerocallis fulva and play important roles in determining leaf size. This study provides valuable transcriptome data for Hemerocallis fulva and establishes a solid theoretical foundation for future cloning and biotechnological breeding efforts targeting leaf size genes. These findings hold great significance for promoting high-quality development within the Hemerocallis fulva industry.