In view of green exploration requirements of national deep geological resources, difficulty in borehole wall protection due to small annulus in extra-deep geological drilling in complex formation, and pollution from waste drilling fluid, an environmentally-friendly high-temperature drilling fluid was developed using high temperature crosslinking and protection technology. Tests showed that after rolling at 150℃, the drilling fluid had good rheological properties, fluid loss reduction, shale expansion suppression, as well as easy degradation (BOD5/CODCr value of 21.5%) and cost-effectiveness. It has broad application prospects in green exploration and geological drilling where strict environmental protection requirements are exercised.