This essay analyses the influence of educational expansion to income distribution with Chinese empirical data,and discusses the mechanism of this influence by two medi-variables:educational distribution and rate of return to education.This research finds that the relationship between educational expansion and income distribution of china is inverted-U,the net impact of educational expansion on income distribution is sum of equality of educational distribution and enhancement of private rate of return to education.The influence of equality of educational distribution to equality of income distribution is positive,but the influence of enhancement of private rate of return to education to equality of income distribution is negative.The net impact of the two influences explains the non-linearity between educational expansion and income distribution.