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Our researches are based on the fact that the systems composed of polyacrylamide and montmorillonite under a kind of shear state often appear in some important practical processes like drilling welletc. The viscosity of polyacrylamide is usually the most important one among the characteristics to decide if the practical processes succeed or not. Therefore, we studied the effect of hydrated montmorillonite on the viscosities of polyacrylamide with temperature and shear rate varying under confined shear by molecular simulation method. Adopting the condition of confi ned shear in the research could make our simulations and the practical processes as similar as possible. First, the model of one polyacrylamide polymer chain with 20 monomers linearly linking surrounded by water molecules between two of montmorillonite layers was constructed. Then canonical ensemble (NVT) MD simulations were carried out for the built model at different temperatures and shear rates. From the gained simulation results, we calculated the polymer’s structural property-radius of gyration, which was directly related to the viscosity property of polyacrylamide polymer. It was found that the viscosity of the polyacrylamide polymer between hydrated clay layers decreased with the temperature increasing from 298 to 343 K under the condition of confi ned shear. The variation trend of viscosity from simulation results was also confi rmed by our experiments. Besides, the viscosity of the polyacrylamide between hydrated clay layers decreased with the shear rate increasing within the range of higher shear rates.