In order to solve many types of public buildings covered building at the same time huge energy problem, and should be energy-saving, but public buildings energy-saving overhead costs library has not been established, the lack of energy-saving issue cost estimates based. Therefore, propose use of the fuzzy neural network method to estimate the cost of energy-saving. Firstly, the energy-saving life cycle should be divided, and the energy-saving life cycle costs should be identified according to the period of full life-cycle; Secondly, the fuzzy neural network to estimate the cost of energy-saving building renovation phase implementation cost estimation model fuzzy neural network; Finally, the actual cases demonstrate the applicability and accuracy of the fuzzy neural network energy saving in the cost estimates.