Through in-depth research and analysis of the historical background, development context, and cultural characteristics of Miao fish patterns, an innovative design method based on extensible semantics and shape grammar was constructed by using fish patterns in wax printing, embroidery, and silver jewelry of the Miao ethnic group in southeastern Guizhou as the research object, with the purpose of providing new ideas for the transformation of fish patterns in contemporary design of the Miao ethnic group in southeastern Guizhou. Firstly, the cultural feature semantics of Miao fish pattern patterns were extracted using literature review, field investigation, and extensible semantics, and an extensible representation model was constructed. Next, the shape grammar was applied to analyze the shape, color, and composition of Miao fish patterns, and based on computer-aided technology, the patterns were inferred and evolved to form new design patterns. Finally, design practice was carried out and the generated fish pattern was subjected to graphic semantic evaluation to ensure the feasibility of the design. By extracting the core semantics of design requirements, various patterns could be induced and deduced to design the matching fish product gift box packaging. Design practice and evaluation could be carried out using methods such as extensible semantics and shape grammar to verify the feasibility of this design path, which has certain reference significance for innovative design of ethnic patterns.