Fuel gauging system is an important subsystem of fuel system, whose accuracy,reliability and maintainability usually have great effect on the performance and capability of the entire aircraft.How to measure the fuel quantity on board in real time and accurately is very important to ensure safety flight and CG management, fuel management,optimizing fuel consuming sequence.Besides,for civil aircraft,improving the accuracy of fuel gauging system will affect the economic of aircraft directly.It is reported that improving the gauging accuracy by 0.5% will result in accommodating several passengers for more.This article analyzed the each kind of error爷s effects on accuracy based on the common error of fuel gauging system,and it placed emphasis on the fuel density measurement爷s influence.It formed the optimal probe combination solution according to the accuracy requirements.