Abstract: M317, a new drilling fluid flow pattern regulator, is developed to solve problems occurred when drilling extend- ed reach wells with water base drilling fluid .such as unsta- ble borehole and poor borehole cleaning. Laboratory performance evaluation shows that its additive level is 1.5%, rolling recovery of Bohai all cuttings 58.7%, and antiswelling rate under high temperature and high pressure 88.5%. When the content of bentonite is given, as the additive level of M317 goes up, dynamic shear and static shear of drilling fluid increase, while apparent viscosity and API water loss almost keep unchanged. When the content of bentonite is at 3.0%-4.5% and the additive level of M317 is within 1.5%~0.5%, the apparent viscosity, dynamic shear and static shear can perfectly meet the technological requirements of extended reach well drilling. The EC50 values of M317 itself and drilling fluid system are over 30000mg/L it is environment-friendly and has been successfully applied in QHD32-6 and JZ-9-3 oilfields in Bohai.