The purpose of the public investment is to serve society and improve people’s living standard, so the social and environmental benefits became the highest standard weighing public investment benefit and a basic starting point of evaluation the public investment project. In this paper, fuzzy mathematics theory was adopted for the comprehensive evaluation on the social, environmental and economic benefits of Land Fund expenditure in Shenzhen，and the process of comprehensive evaluation was improved in order to evaluate the benefits of public investment more efficiently. The calculation result indicated: the proportion change of direct benefit to indirect benefit has negligible effect on total evaluation result; weight and evaluation grade of the social benefit are the highest in 3 types of benefits, the result accords with the tenet of the social benefit that local public investment pursues; weight and evaluation grade of municipal engineering are the highest, accessory facilities—the lowest, the result indicates that the accessory facilities construction of Shenzhen is in the relatively backward.