In view of the problem that the performance of conventional slip-water drag reducer is seriously decreased at high temperature and high salinity，a no-miscible salt-resistant polymer emulsion was developed as a drag reducer. It is necessary to carry out research on the optimization of polymer emulsion formula. Rheology，viscoelasticity，resistance reduction，gel breaking properties，core damage of fracturing fluid prepared with clean water and Ma 18 water were tested in laboratory and field application was carried out. The results showed that，when the concentration of salt-resistant polymer emulsion was 0.05%—1.2%， the viscosity retention rate was between 32.5%—62.5% at high salinity of 21 159.88 mg/L，and the performance of the fracture liquid system at the concentration of 0.2%—0.5% could be similar to that at the concentration of 0.1%—0.2% at low salinity，and the elastic modulus of the system was dominant. The resistance reduction rate of the system was more than 4% higher than that of conventional polymer emulsion. The surface tension of the gel-breaking fluid was less than 28 mN/m，and the interfacial tension with kerosene was less than 2 mN/m，and the residue content was less than 50 mg/L. The damage of gel-breaking fluid to core was less. In field application，the idea of stepping polymer concentration increase was adopted，and it was obtained that when the sand concentration was 30—270 kg/m³，the mass fraction of polymer fracturing fluid should be 0.15% —0.2% ；when the sand concentration was 300—360 kg/m³，the mass fraction of polymer fracturing fluid should be 0.2%—0.35%. The mass fraction of polymer fracturing fluid was further optimized to be 0.15%—0.35%，and the resistance reduction rate could reach up to about 85% during construction. After the test well was put into operation，the effect was good，which provided a reasonable technical scheme for the effective use of polymer fracturing liquid system in horizontal wells of Mahu oilfield.