To investigate the chemical constituents of Buteae Monospermae Semen, the ethyl acetate fraction was separated and purified using column chromatography with silica gel, ODS, MCI, Sephadex LH-20 gel, and semi-preparative HPLC. Structural identification was conducted using modern spectroscopic techniques, including ¹H NMR, ¹³C NMR, and MS. Twenty compounds were identtified as 3R-[(3"S-formyl-β-lactam)ethyl acetate]-hydroxyindole (1), ovalbuminone (2), 2-（3′,4′-dihydroxyphenyl)-1,3-benzodioxol-5-aldehyde (3), lanceolatin B (4), hydroxanthin (5), ovalifolin (6), 2-(2-methoxyphenyl)furo[2,3-h]chromen-4-one  (7), pongapin (8), desmethoxy kanugin (9), 2-(1,3-benzodioxol-5-yl)-3,6-dimethoxy-4H-1-benzopyran-4-one (10),  (2S)-3',4'-methylenedioxy-6",6"-dimethylchromeno-[2",3":7,8]-flavanone (11), 6",6"-dimethylpyrano[2",3":7,8]flavone (12), 3-hydroxyisolanchoearpin (13), 2-(4-hydroxyphenyl)-3-methoxy-4H-chromen-4-one (14), genistein (15), genistein-7-O-β-D-furanosyl-(1→6)-O-β-D-glucopyranoside (16), 1-(4-hydroxy-3-methoxyphenyl)-5-methoxydecan-3-one (17), trans-p-hydroxycinnamic acid (18), ethyl p-hydroxybenzoate (19), and uridine (20). Among them, compound 1 was a new alkaloid, while 20 was also an alkaloid; 2-15 and 17-19 were phenolic acids, and 16 was a phenolic glycoside. Compounds 1-3 and 13-20 were isolated from Buteae Monospermae Semen for the first time. The MTS assay was used to evaluate the effect of compound 1 on cell proliferation. The results demonstrated that compound 1 promoted the proliferation of RAW 264.7 macrophages at concentrations greater than 25.0 μmol/L.