Equality, equity and justice can not include the relations between Gini coefficient and inhabitants' personal income distribution fully. There never any equal income distribution throughout the history of human society, for which the meaning of equality in such concepts as equal or unequal distribution is unclear. Although distribution of social wealth represented by Gini coefficient is determined by inhabitants' personal income distribution, Gini coefficient can't reflect a definite inhabitants' personal income distribution is fair or unfair. Only exchange of equal values in a system of market economy is fair.