The study of the effect of DMSP (dimethylsulfoniopropionate, or dimethyl-beta-propiothetin, DMPT) in the production of acid rain and in the promotion of aquacultural animals nutrition is one of the focus fields in both environmental science and aquaculture. According to previous reports, DMSP is a kind of osmotic substances, mainly in the microalgae, seagrasses and higher plants in sea water. When a organism containing DMSP is dead, the marine microorganisms decompose the DMSP into DMS (dimethyl sulfide) and crylic acid by DMS synthase. The DMS overflows from the surface of the ocean into the atmosphere to cause acid rain. Because DMS can form clouds, it decreases the green house effect. DMSP itself can promote the nutrition metabolism of mammal, poultry, fish and shrimps. It is shown by enzymatic study that two kinds of S-methyltransferases (E.C.220.127.116.11, E.C.18.104.22.168) from animals?livers can transfer S-methyl from DMSP to metabolism in the organism. DMSP, the main osmotic material in marine plants, comes from Methionine. To study the mechanism of DMSP抯 change is of significant value in both marine climate changing and new feed additive applications.