In this study， Lycium barbarum leaves polysaccharide (LBLP) was extracted by alkali extraction and ethanol precipitation. The monosaccharide composition and molecular weight distribution of LBLP were detected by ion chromatography and high performance gel permeation chromatography. The structure of LBLP was characterized by UV spectrum， infrared spectrum and X-ray diffraction. Its antioxidant and lipid metabolism regulation activities were evaluated by free radical scavenging test and enzyme activity inhibition test in vitro. The results showed that the total sugar content of LBLP was (65.78±0.85)%， the protein content was (12.25±0.25)%， and the uronic acid content was (19.26±0.14)%， indicating a protein complex acidic polysaccharide. LBLP was composed of 8 monosaccharides， the molar ratio of which was: narabinose ∶ ngalactose ∶ nrhamnose ∶ nglucose ∶ nxylose ∶ nglucuronic acid ∶ ngalacturonic acid ∶ nglucosamine hydrochloride=427∶293 ∶ 86 ∶ 73 ∶ 42 ∶ 40 ∶ 31 ∶ 8 of which arabinose had the highest content. LBLP mainly contained two polysaccharide components with different molecular weight distributions， among which the component with the highest content had a weight average molecular weight (Mw) of (67 380±288) ku. The UV spectrum showed that the Lycium barbarum leaves extract contains protein absorption peaks， indicating that it was a protein complex polysaccharide， consistent with the protein content determination results. It could be seen from the infrared spectrum that LBLP has the characteristic absorption peak of polysaccharide and contains pyranoside. In antioxidant experiments， LBLP showed good scavenging effects on 2，2-diazo-bis-3-ethylbenzothiazole-6-sulfonic acid cations (ABTS+)， 1，1-diphenyl-2-trinitrophenylhydrazine cations (DPPH+)， superoxide anions， and hydroxyl radicals. When the LBLP mass concentration was 5 mg/mL， the scavenging rates of DPPH+ and superoxide anions reached 90%. In the enzyme activity inhibition experiment， LBLP had good inhibitory ability on the activities of α-amylase， α-glucosidase， trypsin， and pancreatic lipase， and had a dose effect relationship. The IC50 was(23.80±0.17)， (9.53±0.39)， (23.36±0.81) mg/mL and (16.03±0.59) mg/mL， respectively. This study could provide theoretical basis for the development of functional foods related to antioxidant， hypoglycemic， and lipid-lowering effects of Lycium barbarum leaves polysaccharides.