Most of the current temperature-sensitive thickeners are not suitable for high depth reservoirs due to their poor temperature and salt resistance. A self-prepared thermo-sensitive macromonomer（PADA），2-acrylamide-2-methylpropanesulfonic acid （AMPS），N，N-methyl bisacrylamide （MBA） and modified nano-silica （N-np） were used to prepare a kind of nano-silica-thermo-thickening composite N-AMPA by in-situ polymerization. The synthesis conditions of N-AMPA were optimized by orthogonal experiment. The molecular structure of N-AMPA was evidenced by FT-IR and 1H-NMR，and the thermo-thickening behavior，high temperature stability and shear resistance of N-AMPA solution was investigated. The results showed that N-AMPA possessed showed thermo-thickening behavior property in the temperature range of 65—180 ℃，the maximum thickening rate was 94%. The viscosity retention of N-AMPA solution was 68% after high temperature aging at 200 ℃. In 20% NaCl saline solution， the viscosity retention rate was 63%. When the shear rate was 1021 s^-1 ，the solution viscosity reached up to 50 mPa·s. Compared with temperature-sensitive polymer AMPA solution，N-AMPA showed good temperature resistance，salt resistance and strong shear resistance.