In order to study the hypotensive mechanism of combination product of κ-carrageenan and potassium, the effect of low-molecular weight carrageenan potassium (LCP) on intestinal flora regulation was studied using high-throughput sequencing and bioinformatics analysis. Experiments indicated that LCP had a stable and sustained antihypertensive effect on spontaneously hypertensive rats. Compared with that in control group, the final depressurizing amplitude was about 18mmHg (2.3kPa). Through analyzing the types and concentrations of short-chain fatty acids in contents of cecum, it was found that the content of acetic acid, isobutyric acid, and butyric acid in LCP group was significantly higher than that in blank group, and the variation of isobutyric acid production was particularly obvious. The 16S rRNA sequencing results of cecum contents showed that compared with the blank group, the F/B value of the LCP group was reduced, the bacterial abundance was increased, and the number of Ruminococcus which producing butyric acid was dominant. Overall, the results indicated that LCP could be used as a regulator of intestinal microbiota, realized to promote the healthy recovery of intestinal disregulation and therapeutic of hypertension.