Objective To investigate the structural and genetic information of the 5-isomerase/4-reductase gene (PcUER1) of Polygonatum cyrtonema Hua produced in Anhui, China and its expression and regulation mechanism in the biogenic pathway of the monosaccharide rhamnose compounds in Polygonatum cyrtonema Hua. Methods Based on the transcriptome data of Polygonatum cyrtonema Hua, the PcUER1 gene was cloned and a bioinformatics analysis was performed for the cDNA sequence. Quantitative real-time PCR was used to measure the mRNA expression of PcUER1 in different tissues of Polygonatum cyrtonema Hua. Results The cDNA sequence of the PcUER1 gene in Polygonatum cyrtonema Hua was 900 bp in length and encoded 299 amino acids. Sequence analysis showed that Polygonatum cyrtonema Hua had high homology with Ornithogalum caudatum in Liliaceae, with a rate of 92.03%. Quantitative real-time PCR showed the highest mRNA expression of PcUER1 in the root of Polygonatum cyrtonema Hua, followed by fibrous root, stem, and leaf, and there was no significant difference in the mRNA expression of PcUER1 between the leaf and the stem. Conclusion The active site of the PCUER1 gene in Polygonatum cyrtonema Hua contains cofactor binding motif and catalytic tetrad motif, and its protein expression products have stable physical and chemical properties.