This paper focuses on the spatial interpolation methods applied for the small samples of spatial data, which is existed in the process of marine environmental monitoring. The methods of inverse distance weighted interpolation, Spline function, ordinary Kriging interpolation are researched mainly in this text. After the contrast of the distribution diagrams gotten from the test of applying respective method, mainly according to the error analysis, we try to finally pick a method to make a map for the illustration of the seawater environment. Use of a cell dividing method pre-process the raw data, and the default value of sample point blank grid is set to the average of elements of the marine water body. The result, take a distribution map of for example, shows that the application of ordinary Kriging interpolation can reflect the spatial distribution and trends of Shanghai coastal waters more accurately.