NaCl was selected as antifreeze to solve difficulties for drilling and coring in plateau permafrost and exploration process of gas hydrate, and salt tolerant copolymer GTQ and hydrolyzed polyacrylamide PHP were taken as main polymer reagent. With orthogonal test method, 9 groups of optimal formulas were obtained in normal temperature, after low temperature test, the drilling fluid formulation Z1（20%NaCl 0.1%PHP 1.2%GTQ 1%KHm）and Z2 （25%NaCl 0.15%PHP 1.0%GTQ 1%KHm）were determined, which could be used in the temperature of -15℃. The main performance indicators were: AV values were 46.5 and 47.5 MPa·s, PV values were 34 and 35MPa·s, YP values were both 12.8Pa and FLAPI were 6.8 and 7.6mL/30min. By the cost accounting, the 2 formulas are economic and can meet the requirements of plateau permafrost drilling.