A numerical model of fluid-structure coupling dynamic response analysis of a 100 m long pile in deep water in the South China Sea is established based on pool test and verification. The dynamic response characteristics of the long pile in deep water under wave and current loads are calculated and analyzed. The results show that: due to the hydrodynamic nonlinear effect, the numerical analysis results are somewhat conservative; the longitudinal motion and dynamic amplification coefficient of the long pile significantly increase due to the resonance effect caused by the random waves, while the superimposed flow significantly inhibits the motion of the long pile, and the motion decreases by nearly 30%.