The invention relates to a correcting method for a remote sensing reflectivity of vertical inhomogeneous alga water. The method comprises the following steps: calculating the remote sensing reflectivity under the vertical inhomogeneous condition of different alga vertical direction patterns and a corresponding relative error Delta Rrs of the remote sensing reflectivity under the vertical homogeneous condition; establishing a remote sensing reflectivity correcting algorithm for the vertical inhomogeneous alga water according to a relation between the Delta Rrs and the structure parameters of different alga vertical direction patterns; regarding the remote sensing reflectivity of vertical inhomogeneous alga water as the remote sensing reflectivity of vertical homogeneous water. The traditional lake water color remote sensing is established on the basis of the assumption of vertical homogeneous water, but under a practical condition, the change in the vertical direction of the alga in eutrophic lake is large. According to the method provided by the invention, the influence of the vertical inhomogeneous alga water on the application precision of the traditional lake water color remote sensing algorithm can be reduced and the water remote sensing reflectivity under the vertical homogeneous alga distribution condition and the normalized equivalent condition can be acquired.