Quantitative method for social benefit evaluation on land consolidation is put forward based on social security function of land. It has broken through the limitation of current social benefit evaluation on land consolidation, which can only carry out qualitative assessment. Social security of land consolidation includes three aspects of the old-age security, medical security and unemployment security. Functional values of social security, such as the old-age security, medical security and unemployment security, for three types of population (basic population, dependent population and maintenance population) are calculated according to the effective area and original production of arable land. Research result shows that the implementation of land consolidation has brought substantial social benefits. The value of old-age security is still the core, meanwhile the functions of medical security and unemployment security become more and more significant. Quantitative estimation on land consolidation benefits has important function and guiding value on evaluating the effectiveness of land consolidation project and on decision making of investment.