In order to inherit and innovate traditional weft-backed structure jacquard fabric, a design principle and method of digital jacquard with 2:1 weft-backed structure was proposed. Based on the in-depth analysis of the characteristics of the traditional 2:1 weft-backed structure, four digital structural models (A1, A2, B1 and B2) with shaded weave were built by using digital jacquard technology. It lays a theoretical foundation for the creation of four kinds of digital jacquard fabrics with colour shading effects. In addition, the combined application of model A1 and model B1 was taken as an example to illustrate the design method. The resulting fabric had a delicate and natural colour shading effect. And its main and minor motifs were clearly distinguished. Meanwhile, the colour expression was increased while the yarn utilisation and production efficiency were improved. The principle and method proposed in this paper can create a wide variety of digital jacquard fabrics with colour shading effects, which provides ideas for the structural innovation and variety design of traditional jacquard fabrics.