Stomata, small pores on the surfaces of plant leaves and stalks, act as turgor-operated valves to control gas (e.g. water vapor and carbon dioxide) exchange between plant tissues and the atmosphere. Stomata therefore play a major role in the regulation of water and carbon cycling. Generally, plants adapt to changing environments through the combination of multiple traits. The strong relationships between leaf morphological, chemical, and physiological traits have been documented within and across plant species, biomes, and even globally. Despite the importance of leaf stomata, little is known about interspecific covariation in stomatal traits and their relations with other leaf functional traits on a large scale, partly due to a lack of data on leaf stomata in most studies. In the present study, we measured stomatal and leaf functional traits, including stomatal density (SD), stomatal length (SL), specific leaf area (SLA), leaf area (LA), leaf thickness (LT), and nitrogen content (mass- and area-based, N_mass and N_area) of 150 plant species along an altitudinal gradient (540-2357 m) in Changbai Mountain, China. Our results showed that, for all species, the average values of SD and SL were 155.91 stomata/mm² and 34.51 μm, respectively; the average values of SLA, LA, and LT were 33.58 m²/kg, 3291.30 mm², and 0.14 mm, respectively; the mean values of N_mass and N_area were 24.48 g/kg and 1.07 g/m². There were significant relationships between stomatal traits and other leaf functional traits (P < 0.05). Specifically, SD was negatively correlated with SLA, and positively correlated with N_area (P < 0.05); SL was negatively correlated with LA and N_mass, and positively correlated with LT (all P < 0.05). Additionally, SL was negatively correlated with SD (P < 0.05). Standardized major axis (SMA) analysis showed that these significant relationships between stomatal traits and morphological and chemical traits of leaves differed among different altitudes. However, the strong relationship between SD and SL was observed at all altitudes. Furthermore, although no significant difference (P > 0.05) was found among these slopes of SD-SL relationships, the y-intercepts differed significantly (P < 0.05), in which the maximum occurred at 1286 m, and the minimum at 2357 m, indicating plants with larger stomata (higher SL) at any given SD occurred at 1286 m than those with smaller stomata (lower SL) at 2357 m. These findings suggest that there is a covariation between stomatal traits and leaf morphological and chemical traits. However, this may not be universal for all plants due to different stress responses between stomata and other leaf structures. Moreover, the narrow taxonomic range at each altitude may also restrict the expression of bivariate relationships. Future research needs to verify the relationships between stomatal traits and plant functional traits in more plant species from different areas. Finally, our findings highlight the trade-off between SD and SL, which regulates the short-term (plastic) and long-term (evolutionary) strategies in plant adaptation to the external environment. These data provide a basis for revealing adaptation strategies in plants, and help us predict their responses to future climate changes.