Currently,there is no such a method inChina and Europes standards to estimate the conversion between the fuel and electricity consumption in charge sustaining(CS)test for Plug-in hybrid electric vehicles(PHEVs)which are expected to be a possible solution to the shortage of the fossil fuel.In this paper,a methodology is proposed and studied to estimate the "unbiased"(with no charge or discharge)Fuel Economy(FE)in charge sustaining stage.This method utilizes the results from both Condition A and B only.Thus,it offers fuel economy stakeholders a quick and cheap way to estimate the unbiased fuel economy.