As reservoir types and wellbore structures become more diverse and complex，advanced，efficient，and stable EOR techniques and stimulation are critical to achieving cost-effective production of oil and gas resources in complex reservoirs and wells. With its low density，high viscosity，effective protection of oil and gas reservoirs，strong profile control and water plugging ability and perfect oil displacement mechanism，foam has achieved good field application results in drilling and completion， cementing，reservoir protection，reservoir transformation and enhanced oil recovery. Based on the introduction of foam theory，the laboratory studies and field tests of foam fluid in various fields of unconventional oil and gas reservoir development in recent years was summarized，the advantages and disadvantages of enhanced oil recovery and stimulation measures was analyzed，and its future development direction was forecasted.