Objective The relationship between stand structure and undergrowth regeneration seedling was discussed to provide theoretical basis for artificial promotion of natural regeneration.

Method Several Q. mongolica forests in mountainous area of eastern Liaoning province were taken as the research objects, the fitting model and Pearson correlation analysis were used, and the effect of stand spatial structure on natural regeneration of Q. mongolica was studied.

Result (1) The forest stand base area had a significant effect on seedling density. With the increase of stand base area, the seedling density showed an increasing trend. When the base area reached 31 m²·hm⁻², the increase of seedling density gradually slowed down. (2) There was a significant negative correlation between stand base area and seedling base diameter and seedling height (P < 0.05). (3) The relationship between stand competition index and density and seedling density was typical parabola. Compared with density, the effect of competition index on seedling density was more significant. (4) The spatial structure of stand had a significant effect on the species diversity of regenerated seedlings, the higher the degree of mixing, the more complex the vertical structure, and the higher the diversity of regeneration seedling species and Shannon-wiener. (5) Multivariate stepwise regression analysis showed that the main variables influencing the total regeneration density were stand basal area, crowding and competition index.

Conclusion Adjusting stand basal area, crowding and competition index are the effective ways to promote the natural regeneration and improve the species diversity of Q. mongolica forest.