The working principle of infrared sensors is studied and a gas volume fraction measuring device for CO2 is designed

according to Beer-Lambert law and infrared absorption principle.A brief description of the whole architecture of the device is illustrated

including the design of hardware and software.Matlab is used to fit measurement datas of volume fraction ranges from 0 % ～20 %

the correlation coefficient achieves above 0.98.This device can measure the volume fraction of CO2 accurately in real time

and has good stability and small in size.