Isocyanide is an important class of active synthon with a special electronic structure and abundant chemical properties, which can participate in various organic reactions and has a wide range of applications in the efficient synthesis of pharmaceutical molecules, heterocyclic compounds, and natural products, etc. With the development of chemical science, isocyanide-based reactions have been gradually applied from the synthesis of low mass molecules to functional polymers. This review focuses on the recent progress in isocyanide-based step-growth polymerization, as well as the properties and applications of the resultant functional polymers. These polymerizations are divided into six main parts including Passerini polymerization, Ugi polymerization, multicomponent polymerization (MCP) of isocyanide and dialkylacetylenedicarboxylates (DAADs), MCP of isocyanide and green monomer, MCP of isocyanide and industrial waste, as well as the polymerization based on isocyanoacetate. The existing challenges and the promising opportunities are concisely discussed.