When complex formations consisting of anhydrite and salt are drilled, conventional drilling fluid gets readily polluted by anhydrite and salt, leading to reduced fluid performance and viscosity, and even to accidents. In this work, a waterbased drilling fluid system with high calcium and salt tolerance has been developed and its rheological properties, circulating capacity, heat resistance, salt tolerance, calcium tolerance, and solid phase endurance have been calculated. The composition of this system is 3% bentonite + 0.3% Na2CO3 + 5% pregelatinized starch + 0.02% NaOH + 0.3% KRAM + 0.6% PACLV + 0.2% XC + 1% SPF2 + 25% salt. The results show that the performance of this fluid system is stable and its ability to resist pollution is high.