Polyacrylamide and its derivatives have been widely used in oil and gas production；however，their poor salt-tolerance and weak thermostability have impeded their applications in high-temperature and high-salinity oil reservoirs. Thermo-induced viscosifying may be one of the effective solutions for tackling such deficiencies. In this work，a series of nonionic thermoviscosifying copolymers were prepared by copolymerzation of acrylamide and thermo-sensitive macromonomer based on N-（1，1-dimethyl-3-oxobutyl ）-acrylamide ，and the effect of salinity，polymer oncentration，polymer molecular weight ，as well as the nature of the macromonomer on the thermoviscosifying ability of the copolymers was examined. It was found that 0.15% polymer solution could show clear theomoviscosifying ability at82868 mg/L salinity，and the higher the salinity ，or the higher the polymer concentration，the higher the polymer molecular weight ，the stronger the thermothickening ability ；the copolymers based on the macromonomer prepared from a two-step process with acryloyl chloride showed superior thermoviscosifying ability over those from the macromonoer prep ared via one-step coupling reaction.