The sea water eutrophication evaluation as carried out by combining spatial interpolation and nutrition index equation. Three different methods of spatial interpolation such as inverse distance weight, radial basis function, and ordinary kriging methodand and relevant key parameters were compared, using the data of chemical oxygen demand, dissolved inorganic nitrogen and phosphorus of the Jinzhou bay, in August 2009. At the same time, the accuracy of interpolation was verified by cross-validation and the best interpolation method was decided. The results showed that (1) the accuracy of the RBF-TPS is the lowest, while the else have no significant difference. (2) But from the equivalent effect of interpolation surface contours maps, OK method performs better here. At last, OK-EXP method was selected to evaluate eutrophication status, and the result showed that 2.4percent of the investigate area had met the eutrophication level, which the E index exceeded one. Also, the interpolation map could reflect the situation of the eutrophication status correctly and intuitively compared with the traditional eutrophication evaluation method. Thus, it provided a guideline for the practical application of the sea water quality evaluation.