Abstract: This research simplifies a ball-stick model for chain polymers to make their drag reduction mechanism description more visual. It performs direct numerical simulation with fluid flow control equation and polymer constitutive equations, and studies main drag reduction mechanism of polymers based on the simulation results. The polymer's reverse torque under turbulent condition fundamentally inhibits the burst and regeneration of turbulence hairpin vortex, thereby reducing the drag loss of turbulent fluctuation and flow of the fluid. In which the polymer positive torque is acting on the arched head of hairpin vortex and the leg of the second hairpin vortex, inhibiting the burst frequency and intensity of the turbulent vortex, thus reducing the generation of new hairpin vortex. The polymer’s reverse torque is acting in whirling direction of hairpin vortex, which can reduce the curved ratio and tilt angle of the vortex.