In order to analyze the horizontal distribution characteristics of different influence radius preferential flow paths and the spatial associations of biological activity in purple sandstone regions of farmland (vertical soil depths of 10~50cm) in Three Gorges Reservoir Area, the spatial point pattern analysis method (g(r) function) of quantitative ecology was used. After the Monte-Carlo stochastic simulation test, the results showed that the number of preferential flow paths with the same influence radius decreased with the soil depth’s decreasing, while the number of preferential flow paths with different influence radii decreased in the same soil layer. The preferential flow paths with lower influence radii only displayed an aggregated distribution at a small scale (0~20mm). But the aggregated distribution was obviously as the increase of influence radius and scales. The preferential flow paths with different influence radii also displayed an aggregated distribution in deeper soil layer. The preferential flow paths with higher influence radius were more significantly aggregated distribution than those with lower influence radius. The distribution and formation of preferential flow paths were not only influenced by the soil swelling and shrinkage, but also exhibited a positive correlation with animal activity in spatial associations, especially the preferential flow paths with larger influence radius (R≥1.0mm). The spatial point pattern analysis method is simpler than CT and soil water breakthrough curves methods to estimate the preferential flow paths. This proposed method can quantitatively analyze horizontal distribution characteristics of the preferential flow paths with morphology and it is better to reveal the underlying formation process.