Abstract: Considering the poor performance of conventional solid-free drilling fluids in high temperature resistance and environmental protection, research has been conducted for development of viscosifier with desirable heat-resistance and environment-friendly properties. By using starch (ST), acrylamide (AM), 2-acylamido-2-methyl-1-propylsulfonic acid (AMPS), 3-N-(2-methacroyloylethyl)-N,N-dimethylammonio-propane sulfonate (DMAPS), N-vinylpyrrolidone (NVP) and butyl styrene (BS), viscosifier ZNJ-1 has been developed through free radical polymerization. In addition to the characterization of molecular structures, rheological characteristic, suspension capacities and environmental protection performances of the system have been assessed. Lab test results showed that under optimal reaction conditions, ST had a Monomer conversion rate of 86.8% and a grafting rate of 44.8%. After aging of 16 h at 180℃, the ZNJ-1 solution with mass fraction of 1.0% had apparent viscosity of 26.0 mPa·s,plastic viscosity of 17.0 mPa·s, dynamic shearing of 9.0 Pa and static shearing of 3.0 Pa/10.5 Pa. Research results showed that the newly developed ZNJ-1 had outstanding resistance to heat and salt. In addition, the intermolecular hydrophobic associating effects might effectively enhance the suspension stability of the drilling fluid.