Stomata are the main channels for water and gas exchange between plants and their environment; this exchange adjusts the balance between plant carbon assimilation and water loss and reflects to some extent the adaptability of plants to environmental changes. In this study, we investigated stomatal traits in four Quercus species along an elevation gradient (1100-2300 m) in the northern slope of Taibai Mountain (China) and explored the patterns of stomatal traits and responses to environmental variables. The results obtained were as follows. (1) There was a significant positive correlation between the potential conductance index and stomatal density in all species except Q. variabilis. Moreover, a significant positive correlation between stomatal width and length was found in Q. variabilis and Q. aliena var. acuteserrata, whereas a significant negative correlation between stomatal density and length was observed in all species (P < 0.05). (2) The stomatal width and length of Q. variabilis and Q. aliena decreased with altitude while their stomatal density and potential conductance index increased. However, the opposite trends were observed in Q. wutaishansea. Furthermore, along the elevation gradient, the stomatal width of Q. aliena var. acuteserrata decreased and the other stomatal traits showed a single-peak pattern. Particularly, the stomatal length was the shortest at around 1600 m while the stomatal density and potential conductance index reached their maxima. (3) Climate factors had greater influence than soil factors on the variation of stomatal traits along the elevation gradient. For instance, the potential conductance index was mainly positively correlated with atmospheric temperature and air humidity but negatively correlated with precipitation (P < 0.05). Of all the factors considered, air humidity explained the largest percentage (22.9%) of stomatal trait variations. Our results enhance our understanding about the adaptation response of Quercus species to future environmental changes.