A main-chain benzoxazine-based polyfluorene (BluePF-BZ) with T-sensitive fluorescent property was first reported. The mechanism of T-sensitive fluorescent property for BluePF-BZ/E44 + D230 was studied by model simulation. The BluePF-BZ/E44 + D230 possessed high thermal spectral stability and reversible fluorescent response at high temperature. This work will enrich species of T-sensitive fluorescent polymer, and extend scope of polyfluorenes for T-sensitive property.