The invention provides a new method for dividing water injection layer sections of an offshore water injection well. The new method for dividing the water injection layer sections of the offshore water injection well includes the following steps: a step 1, comprehensively considering the permeability gradational difference, the thickness gradational difference, the number of small layers in each layer, the water logging degree of each layer and the pressure difference so as to determine a water injection well layered injection boundary standard through a numerical simulation method; a step 2, counting the number of layers, the sand thickness, the permeability, the water logging degree and pressure distribution of an injection opened layer position of an existing layer section of the water injection well, and calculating the thickness gradational difference and the permeability gradational difference of each water injection layer section; a step 3, performing layer section primary division on the water injection well according to the layered injection boundary standard; and a step 4, considering the water injection process, performing suitable adjustment, and acquiring a final division result. The new method for dividing the water injection layer sections of the offshore water injection well is clear in thinking , is simple to apply, is feasible in offshore and similar oil reservoir water injection well layer section division.