Abstract: Helix stiffened cement mixing piles are widely used in marine soft soil sites due to their excellent seismic and pullout resistance. Firstly, based on the three-dimensional viscous-spring artificial boundary and on equivalent nodal force theory, this paper deduces the equivalent nodal force applicable to the spatial three-dimensional SV wave oblique incidence by considering the effect of delay time. A pile-soil finite element model is established, followed by the loading of spatial SV wave oblique incidence using a Python program. Subsequently, the pile bending moment and pile-soil dynamic p-y curves are analyzed by considering two different directions of incidence (horizontal and vertical). Based on this analysis, the backbone of the dynamic p-y curves is plotted, revealing the mechanism of the dynamic interaction between helical piles and soft soil under a spatial oblique incidence. Finally, the Matlock formula is modified to be applicable to the analysis of dynamic bearing characteristics of helical piles under a spatial oblique incidence. The results indicate that the pile bending moment under an oblique incidence is lower, compared to that under a vertical incidence. Regarding the dynamic p-y curve, the horizontal angle of an oblique incidence affects the magnitude of the hysteresis area, while the vertical angle of an oblique incidence alters the slope of the curve. This study provides a basis for designing the dynamic response of Helix stiffened cement mixing piles in marine soft soil sites.