Abstract: Root tensile properties of vegetation are very important to slope stability. To explore the basic properties of plant roots and influencing factors, we selected Pinus tabuliformis and Larix principis-rupprechtii as our experimental species, classified roots by diameter and storage time, and conducted tensile test indoors at different gauge lengths and different tensile rates. In addition, statistical methods including variance analysis, covariance analysis and multiple regression analysis were used to investigate the relationship between root tensile properties and the influencing factors. The results showed that root diameter had a significantly positive correlation with root tensile resistance of P.tabuliformis and L. principis-rupprechtii and their relation accorded with the power function, but no correlation could be observed between tensile strength and root diameter. Gauge length and tensile rate had significantly negative correlations with root tensile resistance and tensile strength. The root tensile resistance and tensile strength of the two species at different gauge lengths followed a descending order as 50 mm100 mm150 mm200 mm; the root tensile resistance and tensile strength of the two species at different tensile rates descended as 10 mm/min100 mm/min200 mm/min. At the same level of different factors, the mechanical properties of single root of P. tabuliformis were better than those of L. principis-rupprechtii. The regression model about the impact of various factors on the root tensile resistance and tensile strength showed that: 1) root diameter was the main factor affecting the tensile resistance; 2) the impact of gauge length on tensile resistance and tensile strength was greater than the impact of tensile rate; and 3) root storage time had no significant effect on root tensile properties.