Abstract: Dormancy breaking techniques and ultrastructural changes were studied in seeds of Sorbus amabilis Cheng ex Yü. Seeds were under different treatments including various levels of GA3, NaOH, H2SO4, cold stratification and mechanical scarification. The results showed that 90 ％ of the seeds of S. amabilis germinated by mechanical scarification and cold stratification for a period of 75—90 days, which are effective methods to break dormancy. GA3+cold stratification can also break seed dormancy, but less effective than treated with directly cold stratification.Other treatments could not break seed dormancy. Microstructural characters of seed surface and cotyledon cells were observed under scanning and transmission electron microscope in different period of cold stratification, the results showed that germination rate and dormancy breaking effects are directly related to the degree of cuticles broken and disintegration on seed surfaces, and directly related to structural changes and deposition degrade in cotyledon cells.