To study the chemical constituents from the leaves of Camellia longituba Chang.The chemical constituents from the leaves of C. longituba were isolated and purified by normal phase silica gel,reverse phase silica gel,sephedx LH-20 gel,semi-preparative HPLC and HSCCC.The compounds were identified by color,morphology,UV and NMR.Their structures were elucidated on the basis of physico-chemical properties and spectral data.15 compounds were isolated and identified as p-hydroxycinnamic acid (1),quercetin-3-O-β-D-galactoside (2),quercetin (3),catechin (4),protocatechuic acid (5),5,7-dihydroxychromone (6),rutin (7),3-O-methyl quercetin (8),xanthotoxin (9),noreugenin (10) ,naringin (11),kaempferol (12),epicatechin (13),gallic acid (14) and myricetin (15).All compounds were isolated from C. longituba for the first time,and compounds 1,6,7,8,9,10 and 11 were isolated from Camellia for the first time.Compounds 1-15 were screened for urea transporter B (UT-B) inhibitors using red blood cell lysing model.The results showed that compounds 14 and 15 have strong inhibitory activities,with IC₅₀ values of 2.373 and 2.521 μg/mL,respectively.