The phase-transition?temperature of walnut green husk powder was 166.0℃. It was used as water-based drilling fluid additive, and the filtration reduction effect of walnut green husk with powder mesh greater than 120-mesh was slightly better than that of others. The performance evaluation results showed that when the mass fraction of walnut green husk increased from 0 to 1.0%, the apparent viscosity (AV) and plastic viscosity (PV) of drilling fluids waved unremarkably, and the fluid loss (FL) reduced from 12.9 to 7.7 mL, the filtration reduction rate reached to 40.3%. As the treatment temperature increased, AV and PV increased first and then decreased, the effect of reducing fluid loss gradually weakened and lost at more than 160℃. The walnut green husk water extract could obviously inhibit hydration and swelling of clay, and the swelling ratio of calcium bentonite in 0.3%, 0.5% and 1.0% walnut green husk water extract was 50.18%, 46.10% and 39.88%, respectively, which were lower than that of 4.0% KCl solution (56.51%). When the dosage of walnut green husk was 0.3%, the compatibility effect between it and modified starch was better than that between it and polyacrylamide. The former’s viscosity and FL reduced, and the latter’s viscosity increased and FL reduced. The compatibility between walnut green husk and heteropoly glucoside KD-03 drilling fluids was favorable whose FL decreased by 0.6—0.7 mL and the ability of suspension to cuttings, filtration properties and lubricity was improved.