Aiming to read data automatically with digital level,the localization algorithm of the double sinusoid barcode staff was studied according to coding principle that different widths of bar code represent different altitudes of staff,which was used in digital leveling to accomplish automatic staff reading.Based on the relationship of the phase difference and sampling value combination of two sinusoidal signals with position on ruler,two automatic measurements were researched and their numeration formulae were given.One was decoded by Fourier analysis and linear conversion,and the other was decoded by sinusoidal image breadth combination matching and geometrical positioning.Appropriate parameters of sinusoidal signs were designed according to respective decoding means.The results of the simulative barcode reading experiments indicate the feasibility of the algorithms.