Aimed at the problems of strong channeling and high water cut in the mature development stage for horizontal well in low permeability oilfield due to severe heterogeneity of the reservoirs，the composite CO₂ foam huff and puff stimulation technology was studied，a. suitable foam YQY-1 system in CO₂ circumstance was screened，the optimal gas-liquid ratio CO₂ was determined and the water flooding-CO₂ huff and puff-composite CO₂ foam huff and puff was simulated in the laboratory. In addition，the composite CO₂ foam huff and puff technology was used in field. The results showed that the YQY-1 system had good foamability in the CO₂ circumstance. When the CO₂ and YQY-1 system was injected alternately at gas-liquid ratio of 1∶1，the injection pressure of the composite CO₂ foam huff and puff was increased by 1.9 MPa，and oil recovery was enhanced by 11.6%，compared to that of the CO₂ foam huff and puff. In the reservoir conditions，CO₂ foam system could temporarily plug high permeability reservoirs and fractures，and the subsequent gas injection could expand swept volume effectively and initiate the remaining oil in low permeability reservoirs. The results of the composite CO₂ foam huff and puff technology in the field indicated the oil production was increased and the water cut was decreased obviously.