Objective：To study chronic intermittent hypoxia（CIH）-induced ultrastructural damage of hypoglossal motor nucleus in modeling rat. Methods：Twelve adult male Sprague-Dawley（SD）rats（8 weeks old，weighing 180-200 g）were randomly and meanly devided into two groups（the CIH group and the control group），with 6 rats in each group. The control group was fed in atmosphere environment cabins with 21% oxygen. And the rats of CIH group were fed in low oxygen cabins for 8 hours a day for 35 days with 5% to 21% oxygen. We study the ultrastructural damage of hypoglossal motor nucleus in rat under electron microscope. Results：Electron microscopy showed that the cell membrane of the hypoglossal neurons in the normoxic group was continuous，the nuclear membrane was smooth，the chromatin was homogeneous，and the organelles were abundant. In the CIH group，the cell membrane was discontinuous，the shape of nucleus was irregular，and its membrane was invaginated. There were some areas of edema vacuolization in the neurons . The mitochondria are swollen，and its outer membrane is ambiguous；the Golgi body and the smooth endoplasmic reticulum appear to be swollen and dilated；and lipofuscin is also observed. Conclusion：CIH can induce sublingual nucleus damage in rats，so that a series of ultrastructural changes in the hypoglossal nucleus can be observed under electron microscope.