Abstract: The Xuan paper(rice paper),which is white,soft,durable and non-absorbent,is made in an 18-step process from the bark of Pteroceltis tatarinowii and rice straw,and it is entitled as "the king of all kinds of papers".However,the variation of bark quality significantly affects the production size and quality of Xuan paper in China.Based on the investigation,the effects of soil-forming rocks and sprout ages on the bark quality of P.tatarinowii were studied in this paper.The results indicated that significant differences in basic density,fiber length,fiber width,ratio of fiber length to width,cellulose content,lignin content and pentosan content were observed in the barks growing on various soil-forming rocks and in the barks with different sprout ages(α=0.05).Among the above,the basic density of bark ranged from 0.21 to 0.36 g/cm³;fiber length,fiber width,and the ratio of fiber length to width for the bark were 2 181-2 730 μm,9.8-12.0 μm and 184.8-250.5,respectively;while the cellulose content,lignin content and pentosan content were 34.0%-41.0%,9.3%-11.5% and 8.0%-9.8%,respectively.Generally,the bark growing on the soil differentiated from limestone and harvested when the sprout age is three years old is optimal for making Xuan paper.