Regeneration characteristics of three dominant species in a pine-oak mixed forest were conducted in the Qinling Mountains.We analyzed the importance values for seedling and sapling,regeneration dynamics of dominant tree species under different site conditions,including stand density,slope aspect,slope position,and altitude.Our results showed that the stand density,slope aspect,slope position,and altitude had significant effects on the seedling and sapling densities in pine-oak mixed forest.(1)The seedling and sapling densities of Quercus aliena var.acuteserrata and Pinus tabuliformis,respectively,were significantly increased at altitudes of 1 283 m to 1 665 m,whereas the seedling and sapling density decreased significantly at 1 835 m.The seedling and sapling density of P.armandii were significantly higher at altitudes of 1 283 m to 1 835 m.(2)The sapling density of P.armandii and Q.aliena var.acuteserrata decreased gradually from the southwest (20°～75°) in sunny conditions whereas it increased on the shady slopes to the northeast (40°).The seedling densities of three tree species and sapling density of P.tabuliformis increased gradually from the southwest (20°～75°) in sunny conditions and on the shady slopes to the northeast (40°).The seedling densities of Q.aliena var.acuteserrata on the lower slopes were much higher than the middle and upper slopes,whereas the sapling density did not differ.The seedling and sapling density of P.armandii and P.tabuliformis were significantly higher at slopes of lower to upper.The seedling and sapling densities of three tree species increased with the stand density (850 plant·hm^-2 to 1 525 plant·hm^-2) whereas the sapling density was significantly lower in stands (1 900 plant·hm^-2).Thus,enclosing stands on middle altitudes,shady slopes at a moderate density are expected to promote the natural regeneration of pine-oak mixed forest.