In view of the characteristics of high temperature and high salinity heavy oil in Yudong Block of Lukeqin and the unsatisfactory oil displacement effect of XHY-4 foam system applied in the field，the viscosity reduction effect，foam stability，oil resistance，plugging ability and oil displacement effect of DY-2 foam system with heavy oil viscosity reduction were studied and compared with XHY-4 foam system. The experimental results showed that the viscosity of heavy oil could be reduced by 82.5% when the DY-2 solution with an effective content of 0.1% was mixed with heavy oil at a volume ratio of 1∶1. The foam performance of DY-2 foam system was better than that of XHY-4 foam system. The DY-2 foam system could also achieve excellent foam performance while significantly reducing viscosity of heavy oil. The foaming volume of DY-2 foam system with effective content of 0.1% was 445 mL，the foam half-life was 2186 s，the half-life of liquid separation was 96 s，and the foam comprehensive index was 72.96×10⁴ mL·s. The DY-2 foam system had good oil resistance and plugging performance. When the oil content increased from 0% to 20%，the stability of the foam system did not decrease significantly. When the core permeability was 750×10^-3～1250×10^-3μm²，the resistance factor of DY-2 foam system could be stabilized at about 60. In the double-tube displacement experiment， DY-2 was superior to XHY-4 in improving the diversion rate，comprehensive water content and comprehensive recovery degree of high and low permeability pipes. The recovery degree increased by 16.2%，being 4.6 percentage points higher than XHY-4. The DY-2 foam system could better meet the technical requirements of foam flooding to enhance oil recovery in Yudong block.