Analytical procedure for the determination of natural methane hydrates recovered on the Dong Hae sea basin in korea are investigated. The methane hydrates gas collected at different geological sites in the upper matter sediment and water from liberated gas venting sites was analyzed by portable micro gas chromatograph and gas chromatograph equipped with purse discharge detector(PDD) and carboxen(TM) capillary column. The natural hydrate with methane predominant component, and minor/trace amount of CO2, N2 and another hydrocarbons(C2~C5) are measured and evaluated.