Affordable housing construction project belongs to the livelihood, so the focus of the post evaluation of this kind project is whether it achieve the expected social benefits.By discussing post evaluation procedures, contents and methods of the affordable housing construction, it takes the Lingan fourth affordable housing construction project as an example. Using the following methods, such as: social investigation, “before and after comparison”; “with and without comparison”; successful degree evaluation method and others to evaluate social benefit and impact of the Lingan fourth affordable housing construction project, the results show that the project achieve the desired objectives and have good social benefit, at the same time the successful implementation of the project makes the area of humanities and the natural environment improved. Although some problems still exist, it still need appropriate measures to solve.