This paper uses a nationally representative survey data, respectively from the perspectives of the contract right and the use right,to estimate the Gini coefficient of farmland inequality from 1996 to 2013 and explore the mechanism of the evolution. We find: A.Whether from the point of the contract right or the use right, the farmland inequality in China has been gradually expanding. Moreover, there has been a tendency to accelerate in recent years. And the trend of concentration of use right is more obvious. B.For the widening inequality of contract right, the reallocation has been almost prohibited since the second round of the contract, which is the most important institutional factor.And the more frequent farmland taking also has been promoted the extend of farmland inequality in recent year. C.For the widening inequality of use right, it is mainly contributed by the distribution of contract right. The farmland transfer based on market motivation is also improved the centralization of use right.However, it has not been very effective so far and new institutional changes are needed to support it. D. In the long run, the concentration of use right is still subject to the distribution of the contract right and less influenced by other economic factors. The evolution process will be gradual for a long time.