The Gini coefficient is usually used in economics to refer to the "concentration of income distribution". This study uses the Gini Coefficient with the points of Taiwan brokerages to calculate the chip gini coefficient, and then observes the chip gini coefficient by event-study analysis. At extreme values, whether investors can get abnormal returns. The research period is from October 2018 to May 2019. There are 184 trading days in daily data. The samples are divided into three groups: high market value, medium market value and low market value. Empirical evidence shows that the high market value group has short-term significant abnormal returns. The buyer has significant abnormal returns within five days after the event day, while the seller has significant abnormal returns within 11 days after the event day for 3 to 4 days.