Multicomponent polymerization (MCP) is a fascinating synthetic method for the construction of polymers with diverse structures and multifunctionalities. As a rapidly developing field, MCP begins to show great impact in polymer chemistry and polymer materials, which attract scientists attention by their high convenience and efficiency, great structure diversity, high atom economy, and environmental benefit. In this work, a facile one-pot three-component polymerization of diynes, disulfonyl azides, and iminophosphorane is developed to construct N, O, S, and P-containing heteroatom-rich poly(phosphorus amidine)s with advanced functionalities. The optimized MCP proceeds at room temperature in THF under the catalysis of CuI, generating polymers with high molecular weights (up to 85 600 g/mol) in excellent yields (up to 92%). The MCP enjoys general applicability of various monomers including aromatic and aliphatic alkynes, and the only byproduct generated from the polymerization is nitrogen gas, demonstrating high atom economy and environmental benefit. Interestingly, the phosphorus amidine model compounds were found to possess both aggregation-induced emission behavior and thermally activated delayed fluorescence, indicating unique feature of the corresponding polymer materials. The polymers generally enjoy good solubility in polar organic solvents, good film-forming ability, satisfactory thermal stability, and high refractivity. They can also function as fluorescent chemosensors for Pd2+ ions detection with high sensitivity (K-q up to 207 600 M-1) and selectivity. This MCP provides an efficient approach for the synthesis of heteroatom-rich multifunctional polymer materials, which directly construct the luminescent phosphorus amidine moiety in situ, demonstrating high synthetic efficiency and the potential application in material science.