Three new compounds: begonanline (1), nantoamide (2) and methyl (S)-glycerate (3) as well as forty-four known compounds have been isolated and characterized from the rhizomes of Begonia nantoensis. The structures of these compounds were determined by spectral analyses and/or X-ray crystallography. Among them, cucurbitacin B (4), dihydrocucurbitacin B (5), cucurbitacin E (6), dihydrocucurbitacin E (7), cucurbitacin 1 (8), and (-)-auranamide (9) showed cytotoxicity against four human cancer cell lines. 3beta,22alpha-Dihydroxyolean-12-en-29-oic acid (10), indole-3-carboxylic acid (11), 5,7-dihydroxychromone (12), and (-)-catechin (13) demonstrated significant activity against HIV replication in H9 lymphocyte cells.