Abstract: In view of the low efficiency of high circle stimulation in later period of heavy-oil development,a new steam a- gent with high efficiency and its construction technology have been developed.By means of the cooperation of de- composed gas and surfactant,the oil displacement effi- ciency of non-homogeneity core increased by 16.5% on the average.With multi-slug injection and attached steam instilment,this technology has been used in Henan,Shengli and Kelamayi oilfield for more than 120 wells and total efficient rate has reached 92.5%.Field tests prove that the new agent has the advantages on in- creasing the formation energy,improving both the injec- ting steam conformance and oil displacement.It obviously enhances the production of stimulation wells,but fails in wells with high water cut(＞85%)and serious steam channeling.