Abstract: The aim of this study is to find the genes that differentially express between sweet sorghum and common sorghum in the critical period of sweet sorghum sugar accumulation through transcriptome sequencing. Functional analysis of related genes and associated Pathway metabolic pathways were used to further screen the genes related to sugar accumulation and metabolism，which is for laying a solid foundation in fully exploring the biological potential of sweet sorghum and improving sorghum varieties to increase the sugar contents of their stems. In this study，sweet sorghum Liaotian 1 and grain sorghum Xinsu 2 were used as research materials，and their leaf transcriptome data were sequenced and compared at maturity. The 71.98 M reads and 14.54 G total bases were obtained by sequencing. The Cufflinks software was used to assemble the reads，and 1562 new genes were discovered compared with known genetic model. Through differentiated expression，3 115 expressed differential genes were screened，of which 1499 were up-regulated and 1616 were down-regulated. Through GO，COG classification and KEGG pathway enrichment analysis，all of these differentially expressed genes were classified into 94 metabolism pathways covering starch and sucrose metabolism. The five differential genes of β-fructofuranosidase，sucrose synthase and fructokinase from the starch and sucrose metabolic pathway（Pathway ID：Ko00500）were respectively Sb06g031910，Sb06g023760，Sb01g035890，Sb01g033060，and Sb10g0082805 for real-time fluorescence quantitative analysis. The results showed that the expression of these genes at different growth stages was closely related to the activity of their corresponding enzymes，inferring that these genes play a crucial role in the synthesis and accumulation of sucrose in sweet sorghum.

Key words: sweet sorghum, mature leaves, transcriptome, sugar accumulation and metabolism, sucrose