AbstractAs compared to the widely studied linear‐type polyisocyanides (PICs), the development of cross‐linked PICs has not attracted much attention, and their applications in electrochemical fields are scarcely reported by far. Herein, a type of novel fluorene‐based isocyanide monomer (BIF), which bears two isocyano (─NC) groups, is successfully synthesized via Hofmann method with 9, 9‐bis (4‐aminophenyl) fluorene as the precursor. Corresponding fluorene‐based, cross‐linked PIC derivative (PBIF) is successfully prepared by Ni2+‐catalyzed polymerization of BIF. Chemical structure, elemental composition, accumulation state, thermal stability, microstructure, porous characteristics, and specific surface area of PBIF are characterized. NO2− and SO32− electrochemical responses of the modified glassy carbon electrode (PBIF/CS/GCE), which is fabricated with PBIF as the active material and chitosan (CS) as adhesive agent, is systematically analyzed here. Experimental results show that PBIF/CS/GCE exhibits strengthened NO2−/SO32− electrochemical response, suggesting that PBIF has a potential application prospect as novel non‐conjugated polymer‐based NO2−/SO32− electrochemical probing material.