Quercus variabilis Blume (cork oak) and Platycladus orientalis (L.) Franco (arborvitae) are widely used as afforestation tree species in the rocky mountains of northern China, and they play important role in ecological restoration in this region where there are a fragile ecological environment with thin soil depth and remarkable precipitation seasonality due to monsoonal influence. However, in recent years, we found the two species differentially performed on the different slope aspects. In this paper, we measured tree-ring width and the corresponding area increment by dendrochronology, and leaf δ¹³C of the two main afforestation tree species growing on different topographic slope aspects in the dry season. Combining with weather records and the soil moisture, we analyzed the effects of water status on tree growth to study variation in growth of the two species on the different slope aspects. The main purpose is to explore effects of seasonal drought on growth and development of Q. variabilis and P. orientalis forests, and the soil carrying capacity of the forest density. The results showed that the tree-ring width of the two species on shady slopes was significantly greater (P<0.05) than that on sunny slopes. The corresponding basal area increment on shady slopes was also significantly (P<0.05) greater than that on sunny slopes. The δ¹³C values of the two species on sunny slopes were significantly (P<0.05) greater than that on shady slopes, with cork oak 1.17 greater and arborvitae 0.56 greater. In day time, especially at noon, there were higher air temperature, lower relative humidity, and greater vapor pressure deficit (VPD) on sunny slopes than those on shady slopes. The maximum differences in the air temperature, relative humidity, and vapor pressure deficit all occurred at 14:00, by which the air temperature on sunny slopes was 1.5 ℃ higher than that on shady slopes, the relative humidity was 1.6% greater than that on shady slopes, and the VPD was 4.1kPa greater than that on shady slopes. The air temperature on shady slopes in the early morning and evening was slightly higher than that on sunny slopes. The soil moisture on sunny slopes was significantly lower than that on shady slopes in the dry season, however there was no significant difference in the soil moisture between sunny and shady slopes in the wet season. The soil moisture in the dry season was only half of the wet season. Correlation analyses displayed that the precipitation in dry season was significantly (P<0.05) correlated with the annual basal area increment of cork oak, especially on the sunny slope, the correlation coefficient reached 0.7. However, the precipitation in dry season was not significantly correlated to the basal area increment of arborvitae. Those results indicated that drought condition more severely inhibited growth and water use efficiency of cork oak than that of arborvitae, reflecting that there existed variations in tolerance and responsive strategy to drought stress. With shallow soil thickness and low capacity of water storage, the higher evapotranspiration on the sunny slopes exacerbated the adverse effects of drought on tree growth.