A novel polysaccharide, GPH1, was extracted and isolated from ginseng. Structural analysis of GPH1 revealed a molecular weight of 7.321 x 105 5 Da and the presence of glucose and galactose components in a 30.2: 1 molar ratio. Results of methylation and NMR analyses indicated the GPH1 backbone consisted of-*1)-alpha-Glc-(3-* and-*1)-alpha-Glc-(6-*. The anti-obesity activity of GPH1 was assessed by HFD-induced obesity mouse model. GPH1 was found to significantly reduced body weight, alleviated liver lipid accumulation and inflammatory damage. Meanwhile, GPH1 treatment increased the expression of tight junction proteins, including zonula occludens-1 (ZO-1) and claudin-1, while also regulating the intestinal microbiota of obese mice by promoting proliferation of beneficial bacteria with known anti-obesity effects, including s_Akkermansia _ Akkermansia muciniphila, , s_Lactobacillus _ Lactobacillus intestinalis, , s_Lactobacillus _ Lactobacillus reuteri, , s_Streptococcus _ Streptococcus hyointestinalis, , and s_Lactococcus _ Lactococcus garvieae. . Our findings demonstrated that GPH1 is a practical natural dietary supplement with potential therapeutic effects on obesity.