Psathyrostachys juncea is a perennial high-quality forage grass in northern China, which has the advantages of high resistance and high nutrition.Soluble sugar, as an important photosynthetic product, energy reserve substance and osmotic adjustment substance in plants, is not only involved in the regulation of plant growth, development and stress resistance, but also a key indicator to determine forage yield, palatability, energy level and feeding value.In this study, the leaves of Psathyrostachys juncea at different growth stages were used as experimental materials, and the soluble sugar content of leaves at regreening stage, booting stage and post-fruit nutrition stage was measured. The results showed that the soluble sugar content at booting stage was significantly higher than that at regreening stage and post-fruit nutrition stage.The differential expression genes ( DEGs ) were screened by transcriptome sequencing technology to compare and analyze the synthesis-related pathways of different soluble sugar content lines of Psathyrostachys juncea. The results showed that a total of 2830 DEGs were identified in three growth stages, including 351, 531 and 765 unique DEGs in regreening stage, booting stage and post-fruit nutrition stage, respectively, showing obvious growth stage-specific expression characteristics.GO and KEGG enrichment analysis showed that DEGs were mainly enriched in carbohydrate metabolism, protein synthesis, and glucose metabolism-related pathways, among which Pentose phosphate pathway, Glycolysis / Gluconeogenesis, Starch and sucrose metabolism, and Galactose metabolism were the core regulatory pathways. Seven core genes related to glucose metabolism, PGI1, PGI2, HXK1, PFK3, PFK7, FBA2 and PK, were screened out. These genes affect the activity of key enzymes through synergistic regulation or pathway-specific regulation, forming a differentiated soluble sugar accumulation model.The qRT-PCR validation further confirmed the consistency between the expression profiles of these genes and the transcriptome data.The results of this study provide a theoretical basis for revealing the molecular regulation mechanism of soluble sugar accumulation in Psathyrostachys juncea, and also provide candidate gene resources for the subsequent quality improvement of Psathyrostachys juncea and gramineous forage.