UNLABELLED: Patients with Parkinson's disease (PD) with probable rapid eye movement sleep behavior disorder (RBD) (PD-RBD), a specific subtype of PD, are characterized by the presence of more severe motor and non-motor symptoms. This study aimed to elucidate the characteristics and interactions of gut microbiota and plasma metabolic characteristics of PD-RBD, thus screening for the disease mechanisms. A total of 100 PD patients, 50 healthy controls (HCs) and 16 probable idiopathic RBD (iRBD) patients were collected. There were 33 PD-RBD and 67 patients without probable RBD (PD-nRBD) in PD patients. DNA extraction, PCR amplification, and high-throughput sequencing were used for intestinal microbiota analysis, and ultra-high liquid chromatography tandem mass spectrometry was used for metabolome analysis. Spearman analysis was applied to investigate the correlation of fecal microbiota and plasma metabolome. Our findings revealed e ( = 0.017), ( = 0.017), ( = 0.018), ( = 0.035), R-7 group ( = 0.035), and ( = 0.035) were significantly different in PD-RBD, PD-nRBD, and HC. Moreover, the differential metabolites identified in both PD-nRBD and PD-RBD were 3-hydroxy-2-methylpyridine-4,5-dicarboxylate (VIP = 5.802) and 3-methoxy-4-hydroxyphenylglycol sulfate (VIP = 5.732). Furthermore, our analysis revealed that 3-methoxy-4-hydroxyphenylglycol sulfate showed a positive correlation with ( = 0.197, = 0.049). Finally, functional analysis indicated that these distinctive microbiota and metabolites were primarily associated with phenylalanine metabolism and vitamin B6 metabolism. We managed to show that the differential microbiota, differential metabolites, and their interactions in PD-RBD compared to PD-nRBD and HC. This furthers our understanding of disease pathogenesis, and offers fresh perspectives on its detection and treatment. IMPORTANCE: There are currently fewer investigations on the intestinal microbiota and metabolites of probable rapid eye movement sleep behavior disorder (PD-RBD) and idiopathic RBD (iRBD). Our findings indicate that PD-RBD exhibits an increase in and 3-methoxy-4-hydroxyphenethyleneglycol sulfate, and that iRBD exhibits a similar trend. This suggests that the PD prodromal stage may have seen this alteration. Furthermore, functional analysis indicated that these distinctive microbiota and metabolites were primarily associated with phenylalanine metabolism and vitamin B6 metabolism. Basic experiments and multi-center, large-cohort clinical researches are worth conducting to confirm this, since they may offer insights for treating individuals with PD-RBD.