Constipation during pregnancy can induce serious complications, including miscarriage and preterm labour, while the evidence of probiotics in improving constipation during pregnancy was little. In this study, 29 healthy pregnant women and 65 constipated pregnant women were enrolled to assess the effectiveness of probiotics on constipation during pregnancy. Our results showed that the probiotics were effective in improving the Constipation Severity Scale (CSS) and Bristol Stool Scale (BSS) scores, including increasing defecation frequency, decreasing defecation time, and improving fecal characteristics. 16S rRNA sequencing revealed that the probiotics effectively restored the diversity of intestinal microbiota. At the phylum level, Firmicutes (13.27% vs 57.20%) and Actinobacteria (3.77% vs 12.80%) were increased, while Bacteroidetes (77.82% vs 20.24%) was decreased. At the level of the genus, Faecalibacterium (2.03% vs 10.33%), Bifidobacterium (1.21% vs 8.56%), and Phascolarctobacterium (0.05% vs 2.88%), the beneficial bacteria were increased, while the Bacteroides (29.23% vs 12.28%) and Prevotella (24.32% vs 4.92%) were decreased. In conclusion, these results indicated that probiotics can effectively relieve the constipation symptoms by improving the diversity of intestinal microbiota, regulating the disturbance of microflorae, and restoring the balance of microflorae to exert a stronger moderating effect than diet and lifestyle modification. Our results provided clinical data and a theoretical basis for the exploitation of probiotics in treating constipation during pregnancy. Chinese Clinical Trial Registry: ChiCTR2100052069.