The DMPT produced by marine algae is the main biogenic precursor of oceanic DMS. Also, DMPT is an efficient stimulant for growth, feeding, and body movement of fish and striped prawn, and appears to play a physiologic role as an osmoprotectant in algae. This study was focused on the extraction of dimethyl-$eta$-propiothetin as bioactive substance from green seaweed. Identification and quantification of dimethyl-$eta$-propiothetin were measured by headspace gas chromatography after conversion to dimethyl sulfide by treatment with saturated NaOH solution. Dimethyl-$eta$-propiothetin was extracted through various processes(solvent extraction, ultrasonication, boiling and autoclaving) from Enteromorpha intesinalis. The content of dimethyl-$eta$-propiothetin extracted by autoclaving treatment showed higher than those of various extraction methods. Dimethyl-$eta$-propiothetin content in extract of Enteromorpha Enteromorpha was 311,200ng/g after autoclaving at 121$^{circ}C$ for 60min. Dimethyl-$eta$-propiothetin in extract of Enteromorpha intestinalis was comparatively stable under low temperature. The retentions of dimethyl-$eta$-propiothetin content in extract of Enteromorpha intestinalis were 75.8 ~99.8% by incubation at 10~6$0^{circ}C$ for 2 hours. Chemical decomposition of dimethyl-$eta$-propiothetin was observed under laboratory conditions at pH values higher than 9.5.