Ulva pertusa Kjellm is a predominant green algae distributed in the coast of the Bohai Sea, the Yellow Sea, and the East China Sea. It has a long history as a Chinese herbal medicine [1]. It was reported that the extract of U. pertusa showed various biological activities, including antivirus, antioxidant, and reduced blood lipid activity [2, 3]. Several types of secondary metabolites, such as asarones and phytol derivatives, were isolated previously from U. pertusa [4]. In our continuous investigation on marine bioactive natural products, the secondary metabolites were isolated from the ethanolic extract of U. pertusa. We report herein the isolation and structural elucidation of these compounds. Fourteen compounds were isolated from the ethanolic extract by repeated column chromatography, and their structures were identified as uracil (1) [5], adenine (2) [6], cyclo(Ala-Val) (3) [7], cyclo-(Pro-Val) (4) [8], cyclo-(Leu-Pro) (5) [9], uridine (6) [10], guanosine (7) [11], 4-hydroxybenzoic acid ethyl ester (8) [12], vanillin (9) [13], stearic acid (10) [14] and 9,12-octadecadienoic acid (11) [15], cholesterol (12) [16], ergosterol (13) [17], and fucosterol (14) [18] on the basis of their spectra data and comparison with previous literature. Compounds 1–8 and 13 were isolated from U. pertusa for the first time. Preliminary biological evaluation indicated that compounds 3, 4, 6, 7, and 13 showed cytoclasis activities against P-388 cells at a concentration of 50 g/mL. Moreover, compounds 9, 6, and 7 exhibited moderate lethality toward brine shrimp Artemia salina.