Abstract: In order to discuss the dormancy characteristics of Cyclocarya paliurus seeds, the seed coat structure of this tree and its effects on the water permeability were studied. The results showed that in. the seed coat of C. paliurus consists of three layers, i. e., external, middle, and inner seed coat. The epidermis of external seed coat is cutinized, and the middle seed coat is phellem, and the inner seed coat is lignified and hard. All these characteristics show a hindrance and permeability barrier in the seed coat of C. paliurus, preventing the water and gas exchanging and resulting in blocking germination. Compared to the seeds in control, the seeds treated by concentrated sulphuric acid absorbed more water and the speed of water permeation was more quickly. However, the embryos of untreated seeds also absorbed some water in the water absorption experiment.Therefore, the permeability of the seed coat to water may not be a main reason to cause the seed dormancy of C. paliurus. The mechanical restraint of seed coat to radicel growing may be the main reasons.