After analyzing and summarizing previous research, it is obvious that the characteristic parameter, surface spilled oil concentration, is the key limiting condition for the usage of the spilled oil vertical concentration distribution formula, because there are no appropriate field detection condition and measurements. However, the vertical concentration distribution should receive more attention in the environmental risk assessment in consideration of the location of the aquatic organism and the water intakes. Based on the formula of vertical concentration distribution, a mathematic calculation method of the characteristic parameter, spilled oil surface concentration, was put forward, which mainly applies to the stage of surface tension and viscous force for marine oil spill. That is to say we establish the response relationship of the vertical concentration and the surface concentration under the most unfavorable situation by integrating along the vertical direction to get the average concentration. Finally, the key characteristic parameter, surface concentration, is available and it can be used to predict the characteristics of the vertical concentration distribution, which will provide water pollution characteristic parameters for the emergency warning of sea water quality.