Abstract: This paper describes a comprehensive experiment about measuring wire modulus of elasticity by using single-slit diffraction method,which can improve the traditional experimental device.It calculates modulus of elasticity by getting slit width variation，due to the relationship between slit diffraction fringe spacing and slit width,and the amount of change of slit width and the analyte is equal.Using single slit diffraction method to measure the length of the small change can improve the measurement accuracy and reduce the experimental error.