The biggest sea buckthorn(Hippophae rhamnoides) artificial forest in the Asian is located in Jianping County, Liaoning Province, China, which has an important role in controlling soil and water loss. A large area of sea buckthorn in this district died for various reasons in recent years. In order to study the effects of sea buckthorn degradation on soil properties and soil and water loss, the forest's death rate was surveyed by sample plot, and soil physiochemical properties and soil and water loss were measured for different death rates. As the number of sea buckthorn living trees decreased, soil bulk density increased by 1.4%~7.31% and soil porosity and organic matter decreased by 7.81%~21.89% and 9.33%~27.65%, respectively, which shows that sea buckthorn degradation could destroy soil texture and nutrient significantly. The artificial rainfall simulation showed that soil erosion modulus of 539 t/(a·km²) was measured in well grew sea buckthorn forest and it increased with the increase in sea buckthorn death number. Soil erosion modulus reached 1 526 t/(a·km²) when sea buckthorn was almost replaced by elm(Ulmus pumila L.) because of removal of died sea buckthorn. The aggravation of soil and water loss and the deterioration of soil properties damaged soil organic matter and texture, then the death rate of sea buckthorn accelerated, and thus vicious cycle formatted.