A method for measuring linear expansion coefficient of polymer based foam material by using displacement transducer includes fixing measurement zone of material to be measured on two pincer arms of said transducer and setting it in temperature zone of 4.2 ¿C 300 K, connecting resistance foil gauge forming Wheatstone bridge to resistance strain gauge, collecting deformation of material to be measured and clamping force on said transducer then converting displacement amount to be electric amount, sending these data to computer for obtaining curve of strain to temperature variation and furthermore to obtain expansion coefficient of material to be measured from the curve.