Abstract: The study of volume visualization technique for binary variables are the basis of exploring the multi-dimensional and multivariate space visualization. Based on the principle of volume rendering, we map one variable to color and the other to opacity. To prevent the mutual interference of color and opacity, this paper proposes an opacity mapping method utilizing texture sampling. The spatial distribution and relationship of two variables can be observed directly and simultaneously with this method.The proposed method is validated on the temperature and salinity datasets of several seas. Experimental results show that this visualization method can effectively demonstrate the overall distribution features and relationship of the temperature and salinity and facilitate the volume visualization exploration for binary variables.