In response to the deteriorating oil production effect in the deep layers of the heavy oil reservoir in the Ji7 well area of Xinjiang Oilfield after water flooding, with a significant increase in water cut in recent years, and the combined influence of planar and profile contradictions, severe water flooding and water channeling, high crude oil viscosity, and low reservoir utilization efficiency, this paper conducted a formula evaluation study on the profile control system and viscosity reduction system through the idea of profile control + viscosity reduction， and determined the effectiveness of the "profile control + viscosity reduction" system through numerical simulation and field tests.The results show that the developed profile control system（0.35% polymer + 0.35% phenolic crosslinking agent + 0.2% additive A + 0.15% additive B）exhibits a 90-day viscosity retention rate of 70%, viscosity loss of less than 30% under different shear conditions, and a plugging efficiency of over 95% under different permeability conditions, indicating good stability and plugging performance.; the viscosity reduction rate of 0.5% viscosity reducer reaches 95%, and the indoor oil displacement efficiency of the viscosity reduction composite system (0.5% CA301 + 1500 mg/L polymer) is more than 10%. Through numerical simulation of the fluid flow field distribution before and after the treatment, the well group for the field pilot test was selected. Field application shows that after the profile control and viscosity reduction measures, the comprehensive water cut of the well group decreased by 20%, and the daily oil production increased to 20 t/d, with significant results.