Forsythia suspensa is one of the great medicinal herbs. At present, research on the active ingredients of Forsythia suspensa mainly focuses on Forsythin, Forsythiaside and Phillygenol, etc. Polysaccharides show increasingly significant pharmacological functions, which may be associated with the efficacy of Forsythia suspensa in clearing heat and removing toxins and dispersing wind and heat. Therefore, it is important to study the green Forsythiae Fructus polysaccharide and ripe Forsythiae Fructus polysaccharide. In this paper, we have separated and purified green Forsythiae Fructus polysaccharides and ripe Forsythia Fructus polysaccharides by gel chromatography and comparatively analysed the structures of the two groups. Comparison of the anti-inflammatory activity of green and ripe Forsythiae Fructus polysaccharides by lipopolysaccharide (LPS)-induced macrophage hyperinflammation model in RAW264.7 mice, the mechanism of action of polysaccharides with powerful anti-inflammatory activity has also been preliminarily investigated using cellular metabolomics. It was determined that the weight average molecular weight of green Forsythiae Fructus polysaccharide was significantly higher than that of ripe Forsythiae Fructus polysaccharide. The type of monosaccharide that accounted for the largest proportion of the monosaccharide composition of both green and ripe Forsythiae Fructus polysaccharides was Gal-UA, followed by Glc methylation results indicate that the major linkage of both polysaccharides is 4-Gal(p)-UA. The results of the anti-inflammatory activity study demonstrated that both polysaccharides exhibited anti-inflammatory activity, with green Forsythiae Fructus polysaccharide displaying a more powerful anti-inflammatory effect. A metabolomic study identified 18 distinct metabolites in RAW264.7 cells following the action of the active ingredient of green Forsythiae Fructus polysaccharide, compared with the control group. These metabolites were primarily involved in arginine biosynthesis, alanine metabolism, and other pathways that are closely associated with oxidative stress and the inflammatory response. This paper compares the structure and activity of polysaccharides, one of the bases for the medicinal effects of green Forsythiae Fructus and ripe Forsythiae Fructus, and provides a solid foundation for further studies on green Forsythiae Fructus and ripe Forsythiae Fructus.