[Objectives]  To investigate changes in the corpus allatum and glandular cells of silkworm larvae at different stages of development. [Methods]  The corpus allatum was dissected from fourth and and fifth instar larvae of the tetramolter Zhongxian variety of silkworm. Fluorescent images of the corpus allatum and glandular cells were obtained using a fluorescent microscope after dialysis treatment and DAPI staining and combined with an analysis tool to measure the cross sectional area of the corpus allatum and the number of glandular cells. [Results]  The volume of the corpus allatum increased significantly as larvae developed. The number of glandular cells also increased with the development but this was relatively slow. As larvae developed, the volume of glandular cells increased, and the volume of the corpus allatum was significantly correlated with glandular cell size. [Conclusion]  The increase in the volume of the corpus allatum in silkworm larvae is mainly due to the increased volume of glandular cells. The number of glandular cells and the volume of the corpus allatum is closely related to the developmental stage of larvae.