To meet the requirements of high-precision and large-distance digital leveling measurement, a new two-dimensional composite encoding rule for the digital level ruler is proposed in this article. The leveling ruler consists of two column-coded bars, including an absolute-coded bar and a relative-coded bar. The absolute coded column consists of black and white stripes of different widths, and several coded bars along the ruler are combined to form a code segment adopting a binary-decimal coding rule, which uniquely determines the absolute position of the code segment on the ruler. The relative coded column consists of black and white stripes of equal width and relatively large size. The position on the ruler is represented by reference codes that exist simultaneously in the relative coded column and the absolute coded column. According to the proposed coding rules, an accurate reading method for the sight line is designed. The experiments of height difference ,repeatavility and long visual distonce are carned out on teh designed level rkuler. The results show that the measurement time of the 2-D composite code is less than 1. 57 s within 30 m, the barcode recognition rate is 100% , and the maximum deviation is less than 0. 09 mm, which has the advantages of fast, accurate recognition and stability.