Abstract: Aiming at the difficulties of salt-containing paste mudstone, coal seam, hard brittle mudstone and strong formation pore non-uniformity, the normal salt-tolerant polysulfide drilling fluid applied in Pubei area of Tuha oilfield can't solve the problems such as collapse, stuck and redressing in the drilling process. An environment friendly polymer drilling fluid formulated without sulfonated material was tested in Pubei area 3-25 well.The new drilling fluid has good rheological stability, the temperature resistance is up to 120 ℃, the anti-salt calciumis more than 10 000 mg/L, HTHP filtration loss is less than 12 mL, the mud cake viscosity coefficient is between 0.035 and 0.043, and the mud shale rolling recovery rate is over 90%. The field application shows that the GRD polymer environment-friendly drilling fluid can significantly reduce the drilling complex prescription of Pubei area. It is compared with salt-resistant polysulfide drilling fluid, the drilling rate increased by 19.37%, the drilling cycle was shortened by 39.52%, the drilling density decreased by 2.19%, and the diameter expansion rate decreased by 40.86%, no complexity. Cesspool color of the test well is yellowish. The indoor test shows that the slurry is non-toxic and has high biodegradability, slurry EC₅₀ is more than 30 000, and heavy metal content is up to standard, it, which can meet the drilling needs of complex and environment sensitive blocks in Tuha oilfield.