Yanmuxi oilfield of Tuha is a high salinity and mid-low permeability reservoir，which has entered the stage of ultra-high water cut development. In order to improve the oil recovery of the oilfield，the adaptability of polymer solution and reservoir was studied by taking the geological characteristics and fluid properties of the reservoir as the simulation object. The results showed that the relative molecular weight and concentration of polymer affected the compatibility of polymer solution and core. When the mass concentration of polymer was 300—900 mg/L and the relative molecular weight was 800×104—2000×104，the permeability limit of polymer solution was 20 × 10-3—70 × 10-3μm2. When the relative molecular weight of polymer was fixed，the permeability limit increased with the increase of polymer concentration，and the molecular thread size（Dh）increased exponentially. When the polymer concentration was constant，the permeability limit and Dh increased with the increase of polymer molecular weight. According to the relationship between the mid value of core pore radius and Dh，the corresponding compatibility area and plugging area could be obtained. For Yan630 block，the reservoir permeability was 60.5×10-3 μm2 when the percentage of cumulative reservoir thickness reached 60%. The requirement of entering the prescribed reservoir thickness could be met by using polymer solution with relative molecular weight of 1700×104 and concentration of 900 mg/L. If the polymer with lower molecular weight was used，the polymer concentration should be increased accordingly.