This paper uses Lorenz curve and Gini index with adjustment to per capita historical cumulative emission to construct carbon Gini index to measure inequality in climate change area.The analysis shows that 70%of carbon space in the atmosphere has been used for unequal distribution,which is almost the same as that of incomes in a country with the biggest gap between the rich and the poor in the world.The carbon equity should be an urgency and priority in the climate agenda.Carbon Gini index established in this paper can be used to measure inequality in the distribution of carbon space and provide a quantified indicator for measurement of carbon equity among different proposals.