Polydopamine nanoparticles with mesoporous structure (MPDA NPs) were prepared by one-pot method using 1,3,5-trimethylbenzene as template, triblock copolymer PluronicF127 (EO106PO70EO106) as emulsion droplet stabilizer, ethanol as cosolvent and catalyst. Doxorubicin hydrochloride (DOX) was loaded by electrostatic adsorption and the nano drug delivery system was obtained by biomimetic camouflage of platelet membrane. The properties, morphology and particle size of the nanoparticles were characterized by transmission electron microscope, nano particle size analyzer, BET and UV spectrophotometer. The TEM results show that the surface of MPDA had a clear mesoporous structure, and the particle size of PLTM-DOX@MPDA nanoparticles coated by platelet membrane was about 184 nm. The BET results show that the pore size of MPDA was about 45 nm, the pore volume was 0.6232 m3/g, and the specific surface area was as high as 61.181 m2/g. The mesoporous structure supported MPDA as an efficient drug delivery system. The results of drug release in vitro showed that the nano drug delivery system had pH response to control drug release and could achieve sustained drug release. The results of cell uptake assay in vitro show that the nano drug delivery system could avoid phagocytosis of macrophages and actively target cancer cells. The results of cytotoxicity test in vitro showed that the nano-drug delivery system could enhance killing effect of DOX on MDA-MB-231 cells significantly.