Abstract: The water flow in clay nanopores plays an important role in various engineering applications. In this study, we performed non-equilibrium molecular dynamics (NEMD) simulations to investigate the hydrodynamics properties and molecular force mechanisms of clay nanopores. The simulated dynamic viscosity of water was 0.71±0.05 cP and the hydraulic conductivity was (1.79±0.63), (3.23±0.55), and (5.22±0.34) ×10^-11 m/s for h = 3.5, 5.0, and 6.5 nm, respectively. We found that the time-average of total force from clay matrix F^sc basically equals the flow-driving force F^d to maintain a dynamic mechanical equilibrium, so that the water flow can be regarded as equivalent to a simply supported beam with distributed forces acting on it. The driving force f^d, the force of crystal layers f^s, and the force of cations f^c induce the shear strain of pore water, while the force of water molecules f^w can be regarded as an internal viscous force resisting it. The van der Waals barrier above the surface and hydraulic gradient lead to distribution differences in water oxygen atoms, which contribute to a net van der Waals resistance component of f^s. Meanwhile, the water molecules tend to rotate to generate the electrostatic resistance component of f^s and balance the increasing hydraulic gradient. Due to the velocity difference, the water molecules in the slower lamina have a higher tendency to lag and generate a net electrostatic resistance force as well as a net van der Waals driving force on the water molecules in the faster lamina, which together make up the viscous force.