Spar platforms in deep water on both sides suffer from a constant periodic vortex shedding, which will easily induce vortex-induced vibration and reduce the fatigue life. In order to study the influence of section shape of helical strakes on the vortex-induced motions of Spar platform, numerical analysis is carried out for the bare cylinder and Spar platform with different section shapes at Reynolds number Re=3900 by large eddy simulation (LES), including hydrodynamic coefficient and wake flow field. Research shows that the helical strakes are effective in reducing lift coefficient, but will increase drag coefficient, and the circle section strakes are the most efficient which reduced lift coefficient by 94% and increase drag coefficient by 15%. The helical strakes reduce the overall frequency of the vortex shedding and the single frequency is replaced by major and minor frequencies. The circle section has the longest distance before the vortex shedding and has the lowest frequency; and the circle section has the best suppression effect within the range of the research.