Abstract: In order to get the optimum technical parameters of underground coal gasification(UCG) in southern Tianjin,it carry out the model test of UCG by using O2-CO2-sea(fresh)water which belong to the gasification agents,and research the linear function change rule of gasification parameters under the conditions of different contents of oxygen enrichment(40%～100%)and the catalysis of sea water.According to law of conservation of mass,it corrected the test data of UCG model to the optimum oxygen enrichment concentration,and calculated the parameters of export gas in the site.The results show that the optimum oxygen enrichment concentration of UCG using sea water is 80% for the southern Tianjin coal bed and H2 is 31.38%,CO is 34.4%,CH4 is 5.03% and calorific value is 9.6 MJ/Nm3 in the coal gas produced in the site;active component content,calorific value and oxygen enrichment concentration appeared positive correlation while the oxygen enrichment concentration is less than 80%;the active component content and the calorific value appeared slow descending tendency along with increasing of oxygen enrichment while it is more than 80%;sea water as gasification agent is conductive to enhance the calorific value and active component content,which increase 18.62% and 6.88% respectively.