Supercritical Fluid Extract of Angelica (ASFE) shows potential for treating ulcerative colitis (UC) and colorectal cancer. This study prepared ASFE-quaternized chitosan nanoemulsion (ASFE-QCSNE) using low-energy emulsification with quaternized chitosan as the carrier. The formulation was optimized via pseudo-ternary phase diagrams combined with D-optimal mixture design. The physicochemical properties of ASFE-QCSNE were characterized and evaluated, and its in vitro and in vivo anti-inflammatory activities were investigated. The optimized ASFE-QCSNE was identified as an oil-in-water (O/W) emulsion with a particle size of (23.94 +/- 0.53) nm, polydispersity index (PDI) of (0.216 +/- 0.02), and Zeta potential of (23.10 +/- 0.74) mV. Transmission electron microscopy revealed spherical and uniformly distributed droplets. The encapsulation efficiency and drug loading were (96.10 +/- 1.63) % and (2.69 +/- 0.05) %, respectively. ASFE-QCSNE demonstrated favorable centrifugal and preliminary storage stability. In simulated gastric fluid and small intestinal fluid, the nanoemulsion maintained structural integrity, whereas the nanostructure was disrupted in simulated colonic fluid. This suggests that ASFE-QCSNE effectively protects active components in ASFE from gastrointestinal degradation and releases them in the colon. In vitro, ASFE-QCSNE inhibited NO secretion at concentrations of 400-800 mug/mL, demonstrating robust anti-inflammatory activity. In a dextran sulfate sodium (DSS)-induced UC mouse model, ASFE-QCSNE significantly alleviated UC symptoms, as evidenced by increased body weight, reduced disease activity index, improved survival rate, and elongated colon length. Histological analysis revealed intact colonic mucosal structure and reduced inflammatory cell infiltration. Immunohistochemistry indicated upregulated expression of tight junction proteins ZO-1 and Occludin, reinforcing intestinal barrier integrity. Serum cytokine levels showed decreased TNF-alpha and IL-1beta and increased IL-10, consistent with its anti-inflammatory effects. In summary, ASFE-QCSNE exhibits promising therapeutic potential for UC, expanding the applications of ASFE in intestinal diseases.