Relative characteristics of XC and clay are discussed firstly, and the effects of the presence of clay, XC and the polyethylene glycol, and content of XC on drilling fluids are analyzed. The results show the interactions among NaCl, KCl, clay, polyethylene glycol and XC greatly affect the rheological behavior of drilling fluids, and there is a critical temperature in the low-temperature range at which the viscosity of drilling fluids increases rapidly. Adding clay increases viscosity and fluid loss of drilling fluids. With temperature higher than critical temperature, increment of the content of KCl and XC may reduce viscosity, and also...