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Purpose: To prepare and characterize the targeted paclitaxel nanoparticles with biodegradable materials of lactic acid-glycolic acid copolymer modified by folic acid(PLGA-PEG-FA)as the carrier.Methods: The emulsification-dispersion method was used to prepare nanoparticles.The optimum formulation and preparation technology were determined by investigating the influence of the dosage of emulsifiers,organic phase species,aqueous to organic phase ratio,molecular weight of polymer,drug to polymer carrier ratio,and shear speed.Nanoparticles were characterized for the morphology of nanoparticles,particle size,Zeta potential,encapsulation efficiency and drug-loading efficiency.PLGA-PEG-FA(PTX)-NPs and PLGA-PEG(PTX)-NPs were marked by FITC,and their targeting treatment to MCF-7 cells and A549 cells was observed with fluorescence microscope.The interference effect of free folic acid in cell culture medium to PLGA-PEG-FA(PTX)-NPs was observed with fluorescence microscope.The growth inhibiting was studied by CCK-8 test.The apoptosis rate of cells was detected by flow cytometry.Results: PLGA-PEG-FA was successfully synthesized.The targeted nanoparticle was uniform spherical particle,with the particle size was(88.2±6.7)nm,Zeta potential was(56.5±4.2)mV,the encapsulation efficiency was(92.9±3.2)%,and the drug-loading efficiency was(4.8±1.3)%.Compared to PLGA-PEG(PTX)-NPs,MCF-7 cells could swallow PLGA-PEG-FA(PTX)-NPs more effectively(P<0.05).PLGA-PEG-FA(PTX)-NPs and PLGA-PEG(PTX)-NPs couldnt target to A549 cells obviously.Cellular uptake of PLGA-PEG-FA(PTX)-NPs decreased in MCF-7 cells treated with free folic acid prior to the addition of the targeted formulation.In MCF-7 cells,PLGA-PEG-FA(PTX)-NPs showed higher cytotoxicity compared to PLGA-PEG(PTX)-NPs with IC50 values(the drug dose that produces 50%inhibition of growth)of 0.059±0.005 and 0.124±0.03,respectively(P<0.05).The apoptosis rate of MCF-7 cells in PLGA-PEG-FA(PTX)-NPs group(87.04%)was significantly increased compared to PLGA-PEG(PTX)-NPs group(64.14%)after cells were treated for 48h(P<0.05).Conclusion: PLGA-PEG-FA can be utilized in the preparation of surface modified nanoparticles for targeted delivery of anticancer agents to folate-receptor-positive cancer cells.