Secondary forest is the main body of forests in China, and hence, its management plays a very important role in the projects of natural forest conservation and ecological environment construction in this country. The structure, especially the vertical stratification structure of secondary forest is one of the key factors in the management of secondary forest, and can be considered as the base of its management. Based on previous studies, the concept of stratification porosity was introduced, and the optical stratification porosity (OSP), which is the two dimensional alternative measurement of stratification porosity, could be used to represent the vertical stratification structure of secondary forest. The method using hemispherical photographic silhouette (photographic silhouette taken with fisheye lens) to estimate the OSP of a forest stand was also introduced. In addition, the possible applications of OSP in studies on the structure and restoration ecology of secondary forest, and the theory and techniques for the management of secondary forest were also given in this paper.