Abstract: Four mathematic models were established under different premises to enhance the accuracy of Gini coefficient estimation. The estimation of Gini coefficient was performed by designing computer programs for different mathematic models with the help of simulation of Lorenz curve. As an example, the income gaps of urban residents in Henan province from 2003 to 2012 were analyzed in details, and  the results can offer the intellectual and statistic support for government administration and the decision-making sections to measure the income gaps and to adjust the distribution policy and macroeconomic policy