Marine organisms, especially marine microorganisms, have been proven to be a rich source of diverse arrays of bioactive metabolites with great potential for pharmaceutical and medical applications. Marine Bacillus subtilis is a common strain species, which usually produces cyclopeptide, macrolide, indole derivatives, etc. In the course of further studies, 10 diketopiperazines: cyclo(Leu-Ile) (1) [1], cyclo(Leu-Leu) (2) [2], cyclo(Trp-Pro) (3) [3], cyclo(Leu-Pro) (4) [4, 5], cyclo(Phe-Ala) (5) [6], cyclo(Phe-Tyr) (6) [2], cyclo(benzyl-Gly) (7) [7], cyclo(Val-Val) (8) [8], cyclo(Gla-Tyr) (9) [9], cyclo(Ala-Tyr) (10) [10], 1-(4-hydroxyphenyl)ethanone (11) [11], and macrolactin B (12) [12] have been isolated from the marine Bacillus subtilis. Among them, compound 7 is a new natural product. All the compounds have not been reported before from this species.