The experimental project of Young’s modulus measurement is very important in the college physics experiment. In this paper ,the deflection of a simply supported beam is transformed into the change of the width of the slit by means of a single slit diffraction deviec ,and the Young modulus of the beam is obtained. In order to improve the measuring precision and digital degree of the device ,a CCl camera is used to photograph the difiraction spot, and use numerical sot ware to process the photographed pictures to get the width of the diffraction spot and the slit width, so as to get the Young modulus of the object to be measured. The experimental principle of this measurement scheme is clear and reasonable ,and the experimental measurement accuracy is high. Meanwhile , the cross-fertilisation of mechanics and optics can elfectively expand students thinking ability and innovation ability, make students understand the principle of light diffraction and the measurement method of Young modulus more deeply ; at the same time ,the experimental results are obtained by using the numerical software to process the images , which makes the experimental operation more efficient and intelligent.