Study of the spatial patterns of populations can provide many important clues about underlying processes forming these patterns. The population of secondary growth Quercus aliena var. acuteserrata is a representative forest type in the Qinling Mountains. This study was intended to investigate the spatial patterns of secondary Quercus aliena var. acuteserrata forests and to provide a basis for managing natural forests. Two sample plots were established, on a sunny slope and a shady slope, to analyze and compare spatial patterns of Quercus aliena var. acuteserrata population. The pair correlation function and univariate statistics of point patterns were used to analyze the spatial distribution of different development stages and habitats, while bivariate statistics was used to analyze spatial associations of different stages and of different populations on each plot. The change in population spatial pattern and association among different development stages and different populations was compared to explore inherent mechanisms forming the spatial patterns. The results show that spatial distribution patterns and the age structure of the Quercus aliena var. acuteserrata population were different for sunny and shady slopes. The degree of spatial distribution aggregated on the shady slope was higher than that on the sunny slope. The age structure appeared a reverse ‘J’ type on the sunny slope (growing type), while the population renewal was poor on the shady slope (declining type). Initially, different developmental stages showed similar distribution patterns on both slopes, but these became random when young trees matured. Some differences appeared in the relevance of each development stage on each slope. Positive association was observed among developmental stages on the sunny slope, while negative association was observed among developmental stages on the shady slope. For example, on the sunny slope, the distribution patterns of Quercus aliena var. acuteserrata population were positively associated with Populus davidiana, but negatively associated with Bothrocaryum controversum and Carpinus turczaninowii. On the shady slope, the distribution patterns of Quercus aliena var. acuteserrata population were positively associated with Populus davidiana and Toxicodendron vernicifluum, but negatively associated with Bothrocaryum controversum, Acer davidii and Carpinusturc zaninowii. In summary, the distribution patterns of Quercus aliena var. acuteserrata population were basically reasonable on the sunny slope; intraspecific and interspecific competition were not fierce. The distribution patterns within the Quercus aliena var. acuteserrata population were not only influenced by interspecific competition, but were also restricted by intraspecific competition on the shady slope, suggesting that proper thinning could increase light transmittance, thereby improving the regeneration and stability of such Quercus aliena var. acuteserrata population.