Aimed at the heavy oil reservoir of Yu I group in Jin 45 block，thermostability appraisement and injection parameter optimization for self-produced foaming agent system called DQS are carried out，and then noneondensing gas is injected with DQS to improve displacement eficiency for recovering heavy oil during steam flooding in the physical model experiments．The experiment result of DQS shows that the thermostability is still excellent at 300℃．and the suitable foaming density is 1.2％．If N₂ is used as gas source．the gas—liquid ratio should be in the range from 2 to 3 for achieving a relatively large resistance factor and satisfying the requirements of plugging．N₂ and CO₂ selected as noncondensing gas，is injected respectively with DQS during steam flooding in the experiments．The result shows that both could obviously improve oil displacement eficiency．If N₂ is injected with DQS，it is 1 6．7％more than that of steam flooding．If CO₂ is injected with DQS it increases by 1 8．1％in comparison with steam flooding．Economic evaluation result shows that C0₂ is the better choice compared with N₂ to be injected with DQS for improving oil displacement eficiency during steam flooding．