Abstract: In this experiment, the microdissection and the freezing microtomy of the internal sac of aedeagus of longicorn beetles including 3 species belonging to Acalolepta were carried out. Detailed descriptions of the anatomical structure of the internal sac of aedeagus in different species, such as the type of bone valves and chitin area in the basical part, the form, number and distribution of spines (microtrichia)on the wall of the internal sac, and different shape of ejaculatory ampoule connected to the apical part of the internal sac etc, are given in this paper. It is supposed that the chitinization of the apical part of the internal sac, the lateral band of reinforcement contributing to copulation and the ejaculatory ampoule for recollecting sperms are important for the taxonomic and phylogenetic study of the longicorn beetles.