Psathyrostachys juncea is a perennial forage grass widely distributed in northern China. It is well-known of high abiotic stress resistance and high nutritional value. Soluble sugars are small-molecule photosynthetic products， which serve to store energy and regulate osmotic pressure， thereby helping to regulate growth and resist stress.They are key indicators to determine quality， palatability， energy level and feeding value of forage. In this study， the leaves of P. juncea were collected as experimental materials to evaluate the soluble sugar content at spring re-greening stage， summer booting stage and fall tillering stage.The results showed that the leaf soluble sugar content of booting stage was significantly higher than that of other two stages. The differentially expressed genes were screened by transcriptome sequencing to compare and analyze the synthesis-related pathways of different germplasm of P. juncea. The results showed that a total of 2830 differentially expressed genes were identified in three stages， including 531， 765 and 686 unique differentially expressed genes in re-greening stage， booting stage and tillering stages， respectively， showing obvious growth stage-specific expression characteristics. GO and KEGG enrichment analysis showed that differentially expressed genes 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 key regulatory pathways. Seven core genes， 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 seven 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 P. juncea， and also provide candidate gene resources for the subsequent quality improvement of perennial forage grasses.