[Objective] The natural regeneration of Ailanthus altissima in Nankai University were investigated in order to provide the scientific basis for urban natural forest construction and management.[Methods] We used the quadrat sampling method to investigate the quantity, ground diameter and height of A. altissima in Nankai University. The gather intensity indexes including C_x, I, K, m^*, C and I_Δ were used to analyze the spatial distribution pattern of natural regeneration seedling in A. altissima.[Results] (1) A. altissima regenerated naturally in urban greenland. The peak regeneration occurred at seedlings with ground diameter of 2~3 mm. The height level frequency distribution of seedlings showed a "intermittence" type, which was mainly distributed at the height of 2~4 cm.(2) The value of C_x, K, m^*, C, I, I_Δ was 2.24, 1.26, 2.81, 1.79, 1.24 and 1.79, respectively.[Conclusion] Rigid pavement influences the distance of natural regeneration and the spatial distribution of seedlings.