The development of effective strategies for fabrication of fluorescent organic nanoparticles (FONs) with an aggregation-induced emission (AIE) feature has an important impact on the biomedical applications of these AIE-active FONs. In the current work, an ultrafast strategy for fabricating AIE-active FONs is developed through a one-pot microwave-assisted, catalysts-free, and solvent-free Kabachnik-Fields (KF) reaction for the first time. It is demonstrated that such organophosphorous-containing AIE-active block polymers can be synthesized within 2 min under air atmosphere through the microwave-assisted KF reaction. These polymers show amphiphilic properties and can self-assemble into mPEG-CHO-Phe-NH2-DEP FONs, which display high water dispersibility and desirable optical properties. Biological evaluation results suggest that the mPEG-CHO-Phe-NH2-DEP FONs exhibit low toxicity and are potential for biological imaging applications. More importantly, many other multifunctional AIE-active FONs can also be fabricated through the strategy described in this work owing to the universality of KF reaction. Besides, combined with the excellent properties of mPEG-CHO-Phe-NH2-DEP FONs, it is believed that such microwave-assisted KF reaction shall be an effective route for designing various AIE-active nanomaterials for different biomedical applications.