With the continuous research and development of the low-toxic and high-efficiency oil spill dispersants (OSDs), there are an increasing number of evaluation methods of the effect of the OSDs. Currently, the majority of the OSDs effect evaluation is related with the testing of the emulsification in the laboratory, while the stability researches on the OSDs effect are still few. In this paper, the separation characteristics of the oil spill dispersant (OSD) and the oil were investigated, and the stability of the effect of the OSD was also studied. Firstly, the mixture of the oil and the OSD which have been poured into the seawater was thoroughly stirred, left to stand and observed. Later, the greatest separation degree with the oil and the final stability of the OSD was obtained through the analysis. Then, the stability of the combination between the oil and the OSD was studied under the conditions of the no wave, intermittent wave and continuous wave. The study shows the OSD will gradually move away from the oil, which is influenced by the time and duration of the wave action. This study provides experimental basis and methods for the research on the stability mechanism of the OSD effect, as well as the theoretical basis for the comprehensive evaluation and the rational use of the OSD.