The study is carried out the temperature resistance shortage of the clay-free control fluid used in the middle and shallow layer of Jilin field. Polymeric viscosifier,fluid loss additive and the temperature resistance of the control fluid are researched in this paper. The formula of thermostable clay-free control fluid system is also determined: H2O 2.67%GWJ 1.67% ZN-1 2.0%KCl 0.7%A 0.05%BNP-10 0.1%KY-1 2.67% HS-1 a certain amount of NaCl and JZ-1. The temperature resistance is improved from 70℃ to 150℃. The density scope is 1.1g/cm3～1.5g/cm3. It shows great ability on low permeability and low reservoir damage.