This article describes the preparation and analysis of Cd 2+-sensing polydiacetylene-based chemosensors (PDA-MP). Polydiacetylenes (PDAs), a family of conjugated polymers, exhibit a strong response to external stimuli. Accordingly, we have designed a novel PDA sensor, which is linked to mono 2-picolylamine, to increase the PCDA-MP monomer content in polymer system. As a result, it enhanced sensitivity toward Cd 2+ with the low detection limit (2.10 μM) in aqueous solution. Our sequential modification of chelate structure improved the Cd 2+-sensing ability of PDAs. Finally, the interaction between PCDA-MP and Cd 2+ was confirmed by Raman spectroscopy, Field Emission Scanning Electron Microscopes (FE-SEM), and Proton nuclear magnetic resonance (1 H NMR).