Investigation of spatial patterns in forest stands plays a crucial role in comprehending the ecological processes governing the structure of forest communities. Suitable plot scales not only reduce costs and time requirements but also enhance the precise estimation of stand attributes. Additionally, the appropriate degree of sampling scale is important for scientifically evaluating the adjustment of the spatial structure of stands. In this study, we employed a fixed monitoring plot measuring 4 hm² in Pangquangou, Guandi Mountain to evaluate variations in plot size and spatial pattern among major tree species using the plot division method and K2 function. According to the ranking of importance values, we chosed spruce (Picea wilsonii+Picea meyeri), Larix Principis, birch (Betula platyphylla + Betula albosinensis), and the other broad-leaved trees (Sorbus pohuashanensis+Quercus wutaishanica+Populus davidiana+Crataegus kansuensis) as the dominant tree species (group). The findings revealed that a transition in the spatial pattern of the dominant tree species from pronounced intraspecific aggregation to random and uniform distribution, as the plot size decreased (from 4 hm² to 0.25 hm²), with alternated occurrences of aggregation and randomness. Moreover, the agreement indexes of all tree species' subplots exhibited significant deviations from those observed in the reference plot. The highest agreement index values were observed for the species groups of Picea and Larix principis in the combined 1 hm² plots, while the species group of Betula and other broadleaved tree species showed the highest agreement index values in the entire 1 hm² plots. Furthermore, the significant intergroup differences in the agreement index were found between 0.25 hm² plots and combined 1 hm² plots for both Picea/Larix Principis and Betula species groups. Our investigation suggests that 1 hm² plot can serve as the minimum size for assessing the spatial distribution pattern of spruce secondary forests in the study area. The study provides a solid theoretical and technical foundation for investigating the dynamic patterns of spatial distribution in spruce secondary forests and determining appropriate sampling sizes.