To　address　current　medical　challenges,　there　is　an　urgent　need　to　develop　drug　delivery　systems　with　multiple　functions,　such　as　simultaneous　stimuli-responsive　drug　release　and　real-time　imaging.　Biocompatible　polymers　have　great　potential　for　constructing　smart　multifunctional　drug-delivery　systems　through　grafting　with　other　functional　ligands.　More　importantly,　novel　biocompatible　polymers　with　intrinsic　fluorescence　emission　can　work　as　theranostic　nanomedicines　for　real-time　imaging　and　drug　delivery.　Herein,　we　developed　a　highly　fluorescent　nanoparticle　based　on　a　phenylboronic　acid-modified　poly(lactic　acid)　poly(ethyleneimine)(PLA-PEI)　copolymer　loaded　with　doxorubicin　(Dox)　for　intracellular　imaging　and　pH-responsive　drug　delivery.　The　nanoparticles　exhibited　superior　fluorescence　properties,　such　as　fluorescence　stability,　no　blinking　and　excitation-dependent　fluorescence　behavior.　The　Dox-loaded　fluorescent　nanoparticles　showed　pH-responsive　drug　release　and　were　more　effective　in　suppressing　the　proliferation　of　MCF-7　cells.　In　addition,　the　biocompatible　fluorescent　nanoparticles　could　be　used　as　a　tool　for　intracellular　imaging　and　drug　delivery,　and　the　process　of　endosomal　escape　was　traced　by　real-time　imaging.　These　pH-responsive　and　biocompatible　fluorescent　polymer　nanoparticles,　based　on　phenylboronic　acid,　are　promising　tools　for　intracellular　imaging　and　drug　delivery.