A dendrimer PYTPAG2 composed of a central pyrene "core" and four exterior "arms" capped with electroactive triphenylamine is developed as an electroactive precursor to prepare fluorescent films through electropolymerization (EP). The fluorescence emission comes from the central pyrene "core" and the steric hindrance of the exterior "arms" is beneficial for the formation of microporous morphology. The stable and highly cross-linked fluorescent EP films can be obtained even as free-standing films. Further, these dendrimer EP films are first studied as the multifunctional fluorescent probe: the emission of EP films exposed to trinitrotoluene vapor is quenched by 82% in 120 s; while the fluorescence is increased to nearly 400% in 120 s upon exposure to benzene vapor, EP films also act as the fluorescent sensor to Fe3+ in solution and the limit of detection is obtained to be 8.5 x 10(-8) M. All the above detection processes exhibit remarkable reversibility. These excellent performances are attributed to both the specific molecular features of PYTPAG2 and the intrinsic properties of EP films.