The response strategies of twig-leaf traits to resources varied with plant growth. Exploring the variation and correlation of twig and leaf traits of different functional tree species in different diameter classes is of great significance for understanding the variation of plant functional traits within species (diameter class) and between species (shade tolerant) and the response strategy of plants to resources. In Liangshui National Nature Reserve of Heilongjiang Province. Small, medium, and large trees of shade intolerant tree species (Betula platyphylla and Betula costata) and shade-tolerant tree species (Ulmus japonica, Tilia amurensis, and Acer mono) were selected. The volume-based leafing intensity, twig cross-sectional area, twig dry weight, individual leaf area, total leaf area, and total leaf dry weight were measured. One-way analysis of variance (ANOVA) was used to test whether there were significant differences between different diameter classes and different functional types. The method of standardized major axis (SMA) was used to test the effect of diameter class and functional type on the correlation between twig-leaf traits. Result indicates that:all shade-tolerant species had greater twig and leaf traits than shade-intolerant species, except for twig dry weight; all shade-tolerant species had the largest twig cross-sectional area in large trees and the smallest leaf area in middle trees; there were no significant differences in twig dry weight, total leaf dry weight, and the volume-based leafing intensity among different diameter classes of shade-intolerant species, while all shade-tolerant species had significant differences. As the diameter of the tree increases, there is a positive anisotropic growth relationship between twig cross-sectional area and leaf area for different shade-tolerant species, with the exception of shade-tolerant species, where there is a common slope between twig cross-sectional area and individual leaf area; the volume-based leafing intensity and individual leaf area for different shade-tolerant species have a common slope of -0.51 and -0.47, and the anisotropic growth indices of twig cross-sectional area and total leaf area and total leaf dry weight for small and middle trees are significantly different from 1, while large trees are not significantly different from 1. The results showed that different shade-tolerant species and their resource acquisition strategies differ between different diameter classes, with all shade-tolerant species showing a resource acquisition strategy at the small tree stage and a resource conservative strategy at the large tree stage. The shade-intolerant species showed a fast growth strategy compared to the shade-tolerant species, and the difference between shade-intolerant and shade-tolerant species gradually disappeared as the diameter level increased. The results provide a new perspective on intraspecific and interspecific interactions during forest succession.