With the rapid development of UHV power grid, social benefits as part of economic benefits can not accurately assess the social benefits of UHV power grid. In order to accurately assess the social benefits of UHV power grid, social benefits assessment model is introduced. Social cost and social benefits assessment index are provided in model, from vertical and horizontal social benefits of the three options are assessed through comparative assessment methods, scientificity and particularity for social benefits of UHV can be reflected through vertical and horizontal assessment. At last, the evaluation model and method is verified and analyzed through the analysis of engineering projects.