Abstract:The fluctuating asymmetry (FA) of biological development stability has a close relationship with environmental conditions. The Ligustrum lucidum and L. quihoui were selected as experimental materials, which are commonly urban greening tree species in Xi’an. The mature leaves of these plants were sampled from 9 air environmental monitoring sites. The leaf halfperimeter, halfwidth, and halfarea were measured and the each FA was calculated, which the vein is symmetry axis. The response characteristics of 2 kinds leaf FA to envrionmental air condition were researched, and the potential of leaf FA as an air quality indicator was explored. The values of fluctuating asymmetry of perimeter, width, and area (abbreviated as FAP, FAW and FAA, respectively) were 0.051, 0.063 and 0.082 for L. lucidum, respectively. The FAP, FAW and FAA of L. quihoui were 0.043, 0.082 and 0.102, respectively. The each FA showed significant differences between different plant species sampling sites and enviromental sites. There were close relationship between the FAP and air SO2 concentrations for each plant species. The leaf FA has high sensitivity to different environmental conditions, and it has the potential as a biological monitoring indicator. However, the choice of suitable species for monitoring, leaf characteristic indexes, the number of samples, FA and characteristics of pollutants relations should further research.