Artificial vegetation was set up on the slope in the Zhuozi County section of Hohhot-Jining expressway in 2003 and 2004.By contrast to bare slope,soil properties have changed remarkably and have increased with plantation time.A comprehensive evaluation index system for soil quality based on soil physical,chemical,and biological properties is established.Based on the system method and multivariate statistics,the changes of soil quality during soil formation on expressway slope are evaluated.The work is expected to reveal the changes of soil quality and the coupling relationship between vegetation and soil.Using SPSS analysis software,the membership function value,component capacity,and weights of soil quality factors by PCA are calculated and then the SQI(soil quality index) values for all plots are calculated.Results show that soil quality has increased since artificial vegetation was set up.The SQI values indicate that soil quality does not change with the time of artificial vegetation extending.Because management measures are different annually and artificial vegetation does not form a steady community,the SQI value for 2-year plantation plot is higher than that for 3-year plot.Among all plots,the highest SQI value is 0.649,which is distinctly higher than other plots.