Abstract: The reasonable value of single layer ice thickness is important for sea ice disaster risk assessment to ocean engineering.The design value of single layer ice thickness for JZ20-2 sea area was calculated based on field measured data, utilizing statistical analysis, sea ice zoning design conditions and the negative accumulated temperature method.Then the calculation results, feasibility and safety of the three methods were evaluated.Results show that, for the sea ice risk assessment of China, the sea ice zoning method and the statistics analysis method were proposed to used to determine the design value of the single layer ice thickness.