Abstract: The aim of this study was to prepare and characterize Eucommia ulmoides polysaccharide nanoparticles (EUP NPs) and investigate their anti-inflammatory in vitro. Amphiphilic Eucommia ulmoides polysaccharide nanoparticles loaded with quercetin (QT/LA-EUP NPs) were prepared using the anti-solvent precipitation method. The stability of the nanomaterial was characterized through the measurement of particle size, polydispersity index (PDI), and Zeta potential. The structural characterization of the nanoparticles was conducted by transmission electron microscopy, UV-VIS spectroscopy, Fourier transform infrared spectroscopy, and other methods. The antioxidant capacity of the material was tested by measuring its ability to scavenge DPPH and ABTS⁺ radicals. The anti-inflammatory activity of the nanoparticles was evaluated by establishing a lipopolysaccharide (LPS)-induced inflammation model in RAW264.7 macrophages. The results indicated that the encapsulation efficiency of LA-EUP NPs for quercetin reached 70.4%±2.4%, with a loading capacity of 5.6%±0.2%. The particle size and polydispersity index (PDI) of the nanoparticles were almost unaffected by different pH levels and storage durations. Additionally, the quercetin release rate increased with increasing glutathione concentration, although this was not the primary focus of the study. The DPPH and ABTS⁺ radical scavenging assays demonstrated that QT/LA-EUP NPs exhibited good antioxidant capacity within a certain concentration range. Furthermore, QT/LA-EUP NPs significantly alleviated the decrease in RAW264.7 macrophage viability caused by LPS and inhibited the production of nitric oxide (NO). In this study, QT/LA-EUP NPs with good stability are successfully prepared, which have good antioxidant activity and can reduce the damage of inflammation induced by LPS. QT/LA-EUP NPs are expected to be used in nano-delivery systems of food functional factors.