The chemical constituents of Streptomyces sp. P325 were investigated. The ethyl acetate extract of its fermentation broth was separated and purified using various chromatography techniques,including silica gel column,ODS reverse gel column,Sephadex LH-20 column,and semipreparative HPLC.Six compounds were isolated,and their structures were identified by spectral data analysis and literature comparison,including two new compounds,tetrahydroxy-octadecanoic acid I (1) and tetrahydroxy-hexadecanedioic acid I (2),as well as four known compounds:iso-frenolicin B (3),（R）-7-acetyl-3,6-dihydroxy-8-propyl-3,4-dihydronaphthalen-1(2H)-one (4),methyl p-hydroxybenzoate (5),and isonicotinaldehyde (6).The isolated compounds 1-6 were evaluated for cytotoxic activities.The results indicated that compound 3 exhibited significant inhibitory activity against HepG2 cells with an IC₅₀ of 13.11 μmol/L. Compound 3 showed a moderate growth inhibitory effect against Hela cells with an IC₅₀ of 25.04 μmol/L.