A novel visualized sound description, called sound dendrogram is proposed to make manual annotation easier when building large speech corpora. It is a lattice structure built from a group of "seed regions" and through an iterative procedure of mergence. A simple but reliable extraction method of "seed regions" and advanced distance metric are adopted to construct the sound dendrogram, so that it can present speechs structure character ranging from coarse to fine in a visualized way. Tests show that all phonemic boundaries are contained in the lattice structure of sound dendrogram and very easy to identify. Sound dendrogram can be a powerful assistant tool during the process of speech corporas manual annotation.