Abstract: The Lorenz curve is widely used in economics to describe inequality in wealth.In recent years,the Lorenz asymmetry coefficient and Gini coefficient derived from Lorenz curve have been used to describe inequality in plant size and other characteristics in plant ecology instead of Skewness coefficient.Like other important ecological indexes, the precision and bias of Lorenz asymmetry coefficient and Gini coefficient can be estimated using the Jackknife and Bootstrap resampling techniques.The estimating of bias and standard error of Gini coefficient by the Jackknife and Bootstrap procedures and five different methods used to construct bootstrap confidence intervals were summarized in this paper.We took the experiment results of 10 natural populations of Iris hexagona under salinity stress from University of Louisiana at Lafayette as an example to illustrate the biological meaning of Gini coefficient.Gini coefficients and it’s bias and standard errors of fives quantitative traits including aboveground biomass, belowground biomass,total biomass,number of flowers and number of seeds were estimated using GINI2003(1.0 for WINDOWS) developed by us.We found that salinity decreased the aboveground biomass,belowground biomass and total biomass of Iris hexagona(by the mean value) but increased the inequality of them(by the Gini coefficient) under salinity stress.However,salinity decreased the inequality of the number of seeds.The number of seeds increased under salinity stress(by mean),but Gini coefficient illustrated that the increase of the number of seeds in total due to the increase of the equality.We also found that the inequality coefficients of reproduction traits were larger than that of growth traits.Changes in the inequality of plant size involve many genetic and ecological factors.Modern molecular techniques like quantitative traits Loci especially the interaction with environment can be used for further exploring the essence of inequality of plant quantitative traits.