Changes in the intestinal microbiota are known to occur in constipated patients. Dietary fiber restriction presents obstacles to appropriate defecation and affects fecal properties, but the relationship between fecal microbiota and fecal morphological properties remains obscure. Therefore, we examined the influence of fiber diets on the fecal microbiome and properties in rats, and the effectiveness of the Japanese traditional medicine Junchoto (JCT) in rats with fiber deficit-induced constipation. Rats were fed three different fiber diets with varying cellulose contents (0 %, FFD; 5 %, ND; 15 %, HFD), respectively, as follows: study 1: 21 days of feeding; study 2: 14 days of feeding followed by 7 days of ND (fiber normalization in all groups); study 3: FFD for 21 days, followed by JCT administration from 14 days. Fecal properties and 16S rRNA amplicon sequencing results were examined. We observed that the fecal frequency, dry weight, and length were increased, and water ratio were decreased in a cellulose dose-dependent manner. The difference in several kinds of fecal microbiota, but not the α-diversity Chao1 index and the Firmicutes / Bacteroidetes ratio (F/B ratio), between groups were observed. The change in fecal property in both the HFD and FFD groups was ameliorated with fiber normalization, accompanied by alteration of the Chao1 index and/or F/B ratio. JCT administration reversed the fecal morphological changes in FFD group, accompanied by F/B ratio increasing. In conclusion, short-term dietary changes modulated microbial homeostasis, which is linked to fecal property. JCT may alter the F/B ratio and improve fecal properties to facilitate easier excretion.